refactor(ci): Consolidate Rust checks with optimised toolchain setup

Merge rust-checks.yml into prek-checks.yml for a unified workflow that
runs formatting and clippy/test checks in parallel jobs.

Add reusable composite actions:
- setup-rust: Smart Rust toolchain management with caching
  * Uses cargo-binstall for pre-built binary downloads
  * Integrates Mozilla sccache-action for compilation caching
  * Workspace-relative paths for better cache control
  * GitHub token support for improved rate limits
- setup-llvm-with-apt: LLVM installation with native dependencies
- detect-runner-os: Consistent OS detection for cache keys

Key improvements:
- Install prek via cargo-binstall --git (crates.io outdated at v0.0.1)
- Download timelord-cli from cargo-quickinstall
- Set BINSTALL_MAXIMUM_RESOLUTION_TIMEOUT=10 to avoid rate limit delays
- Default Rust version 1.87.0 with override support
- Remove redundant sccache stats (handled by Mozilla action)

Significantly reduces CI runtime through binary downloads instead of
compilation while maintaining all existing quality checks.

.forgejo/actions/detect-runner-os/action.yml

@@ -0,0 +1,39 @@
+name: detect-runner-os
+description: |
+  Detect the actual OS name and version of the runner.
+  Provides separate outputs for name, version, and a combined slug.
+
+outputs:
+  name:
+    description: 'OS name (e.g. Ubuntu, Debian)'
+    value: ${{ steps.detect.outputs.name }}
+  version:
+    description: 'OS version (e.g. 22.04, 11)'
+    value: ${{ steps.detect.outputs.version }}
+  slug:
+    description: 'Combined OS slug (e.g. Ubuntu-22.04)'
+    value: ${{ steps.detect.outputs.slug }}
+
+runs:
+  using: composite
+  steps:
+    - name: Detect runner OS
+      id: detect
+      shell: bash
+      run: |
+        # Detect OS version (try lsb_release first, fall back to /etc/os-release)
+        OS_VERSION=$(lsb_release -rs 2>/dev/null || grep VERSION_ID /etc/os-release | cut -d'"' -f2)
+
+        # Detect OS name and capitalise (try lsb_release first, fall back to /etc/os-release)
+        OS_NAME=$(lsb_release -is 2>/dev/null || grep "^ID=" /etc/os-release | cut -d'=' -f2 | tr -d '"' | sed 's/\b\(.\)/\u\1/g')
+
+        # Create combined slug
+        OS_SLUG="${OS_NAME}-${OS_VERSION}"
+
+        # Set outputs
+        echo "name=${OS_NAME}" >> $GITHUB_OUTPUT
+        echo "version=${OS_VERSION}" >> $GITHUB_OUTPUT
+        echo "slug=${OS_SLUG}" >> $GITHUB_OUTPUT
+
+        # Log detection results
+        echo "🔍 Detected Runner OS: ${OS_NAME} ${OS_VERSION}"

.forgejo/actions/setup-llvm-with-apt/action.yml

@@ -0,0 +1,167 @@
+name: setup-llvm-with-apt
+description: |
+  Set up LLVM toolchain with APT package management and smart caching.
+  Supports cross-compilation architectures and additional package installation.
+
+  Creates symlinks in /usr/bin: clang, clang++, lld, llvm-ar, llvm-ranlib
+
+inputs:
+  dpkg-arch:
+    description: 'Debian architecture for cross-compilation (e.g. arm64)'
+    required: false
+    default: ''
+  extra-packages:
+    description: 'Additional APT packages to install (space-separated)'
+    required: false
+    default: ''
+  llvm-version:
+    description: 'LLVM version to install'
+    required: false
+    default: '20'
+
+outputs:
+  llvm-version:
+    description: 'Installed LLVM version'
+    value: ${{ steps.configure.outputs.version }}
+
+runs:
+  using: composite
+  steps:
+    - name: Detect runner OS
+      id: runner-os
+      uses: ./.forgejo/actions/detect-runner-os
+
+    - name: Configure cross-compilation architecture
+      if: inputs.dpkg-arch != ''
+      shell: bash
+      run: |
+        echo "🏗️ Adding ${{ inputs.dpkg-arch }} architecture"
+        sudo dpkg --add-architecture ${{ inputs.dpkg-arch }}
+
+        # Restrict default sources to amd64
+        sudo sed -i 's/^deb http/deb [arch=amd64] http/g' /etc/apt/sources.list
+        sudo sed -i 's/^deb https/deb [arch=amd64] https/g' /etc/apt/sources.list
+
+        # Add ports sources for foreign architecture
+        sudo tee /etc/apt/sources.list.d/${{ inputs.dpkg-arch }}.list > /dev/null <<EOF
+        deb [arch=${{ inputs.dpkg-arch }}] http://ports.ubuntu.com/ubuntu-ports/ jammy main restricted universe multiverse
+        deb [arch=${{ inputs.dpkg-arch }}] http://ports.ubuntu.com/ubuntu-ports/ jammy-updates main restricted universe multiverse
+        deb [arch=${{ inputs.dpkg-arch }}] http://ports.ubuntu.com/ubuntu-ports/ jammy-security main restricted universe multiverse
+        EOF
+
+        echo "✅ Architecture ${{ inputs.dpkg-arch }} configured"
+
+    - name: Start LLVM cache group
+      shell: bash
+      run: echo "::group::📦 Restoring LLVM cache"
+
+    - name: Check for LLVM cache
+      id: cache
+      uses: https://github.com/actions/cache@v4
+      with:
+        path: |
+          /usr/bin/clang-*
+          /usr/bin/clang++-*
+          /usr/bin/lld-*
+          /usr/bin/llvm-*
+          /usr/lib/llvm-*/
+          /usr/lib/x86_64-linux-gnu/libLLVM*.so*
+          /usr/lib/x86_64-linux-gnu/libclang*.so*
+          /etc/apt/sources.list.d/archive_uri-*
+          /etc/apt/trusted.gpg.d/apt.llvm.org.asc
+        key: llvm-${{ steps.runner-os.outputs.slug }}-v${{ inputs.llvm-version }}-v3-${{ hashFiles('**/Cargo.lock', 'rust-toolchain.toml') }}
+
+    - name: End LLVM cache group
+      shell: bash
+      run: echo "::endgroup::"
+
+    - name: Check and install LLVM if needed
+      id: llvm-setup
+      shell: bash
+      run: |
+        echo "🔍 Checking for LLVM ${{ inputs.llvm-version }}..."
+
+        # Check both binaries and libraries exist
+        if [ -f "/usr/bin/clang-${{ inputs.llvm-version }}" ] && \
+           [ -f "/usr/bin/clang++-${{ inputs.llvm-version }}" ] && \
+           [ -f "/usr/bin/lld-${{ inputs.llvm-version }}" ] && \
+           ([ -f "/usr/lib/x86_64-linux-gnu/libLLVM.so.${{ inputs.llvm-version }}.1" ] || \
+            [ -f "/usr/lib/x86_64-linux-gnu/libLLVM-${{ inputs.llvm-version }}.so.1" ] || \
+            [ -f "/usr/lib/llvm-${{ inputs.llvm-version }}/lib/libLLVM.so" ]); then
+          echo "✅ LLVM ${{ inputs.llvm-version }} found and verified"
+          echo "needs-install=false" >> $GITHUB_OUTPUT
+        else
+          echo "📦 LLVM ${{ inputs.llvm-version }} not found or incomplete - installing..."
+
+          echo "::group::🔧 Installing LLVM ${{ inputs.llvm-version }}"
+          wget -O - https://apt.llvm.org/llvm.sh | bash -s -- ${{ inputs.llvm-version }}
+          echo "::endgroup::"
+
+          if [ ! -f "/usr/bin/clang-${{ inputs.llvm-version }}" ]; then
+            echo "❌ Failed to install LLVM ${{ inputs.llvm-version }}"
+            exit 1
+          fi
+
+          echo "✅ Installed LLVM ${{ inputs.llvm-version }}"
+          echo "needs-install=true" >> $GITHUB_OUTPUT
+        fi
+
+    - name: Prepare for additional packages
+      if: inputs.extra-packages != ''
+      shell: bash
+      run: |
+        # Update APT if LLVM was cached (installer script already does apt-get update)
+        if [[ "${{ steps.llvm-setup.outputs.needs-install }}" != "true" ]]; then
+          echo "::group::📦 Running apt-get update (LLVM cached, extra packages needed)"
+          sudo apt-get update
+          echo "::endgroup::"
+        fi
+        echo "::group::📦 Installing additional packages"
+
+    - name: Install additional packages
+      if: inputs.extra-packages != ''
+      uses: https://github.com/awalsh128/cache-apt-pkgs-action@latest
+      with:
+        packages: ${{ inputs.extra-packages }}
+        version: 1.0
+
+    - name: End package installation group
+      if: inputs.extra-packages != ''
+      shell: bash
+      run: echo "::endgroup::"
+
+    - name: Configure LLVM environment
+      id: configure
+      shell: bash
+      run: |
+        echo "::group::🔧 Configuring LLVM ${{ inputs.llvm-version }} environment"
+
+        # Create symlinks
+        sudo ln -sf "/usr/bin/clang-${{ inputs.llvm-version }}" /usr/bin/clang
+        sudo ln -sf "/usr/bin/clang++-${{ inputs.llvm-version }}" /usr/bin/clang++
+        sudo ln -sf "/usr/bin/lld-${{ inputs.llvm-version }}" /usr/bin/lld
+        sudo ln -sf "/usr/bin/llvm-ar-${{ inputs.llvm-version }}" /usr/bin/llvm-ar
+        sudo ln -sf "/usr/bin/llvm-ranlib-${{ inputs.llvm-version }}" /usr/bin/llvm-ranlib
+        echo "  ✓ Created symlinks"
+
+        # Setup library paths
+        LLVM_LIB_PATH="/usr/lib/llvm-${{ inputs.llvm-version }}/lib"
+        if [ -d "$LLVM_LIB_PATH" ]; then
+          echo "LD_LIBRARY_PATH=${LLVM_LIB_PATH}:${LD_LIBRARY_PATH:-}" >> $GITHUB_ENV
+          echo "LIBCLANG_PATH=${LLVM_LIB_PATH}" >> $GITHUB_ENV
+
+          echo "$LLVM_LIB_PATH" | sudo tee "/etc/ld.so.conf.d/llvm-${{ inputs.llvm-version }}.conf" > /dev/null
+          sudo ldconfig
+          echo "  ✓ Configured library paths"
+        else
+          # Fallback to standard library location
+          if [ -d "/usr/lib/x86_64-linux-gnu" ]; then
+            echo "LIBCLANG_PATH=/usr/lib/x86_64-linux-gnu" >> $GITHUB_ENV
+            echo "  ✓ Using fallback library path"
+          fi
+        fi
+
+        # Set output
+        echo "version=${{ inputs.llvm-version }}" >> $GITHUB_OUTPUT
+        echo "::endgroup::"
+        echo "✅ LLVM ready: $(clang --version | head -1)"

.forgejo/actions/setup-rust/action.yml

@@ -0,0 +1,236 @@
+name: setup-rust
+description: |
+  Set up Rust toolchain with sccache for compilation caching.
+  Respects rust-toolchain.toml by default or accepts explicit version override.
+
+inputs:
+  cache-key-suffix:
+    description: 'Optional suffix for cache keys (e.g. platform identifier)'
+    required: false
+    default: ''
+  rust-components:
+    description: 'Additional Rust components to install (space-separated)'
+    required: false
+    default: ''
+  rust-target:
+    description: 'Rust target triple (e.g. x86_64-unknown-linux-gnu)'
+    required: false
+    default: ''
+  rust-version:
+    description: 'Rust version to install (e.g. nightly). Defaults to 1.87.0'
+    required: false
+    default: '1.87.0'
+  sccache-cache-limit:
+    description: 'Maximum size limit for sccache local cache (e.g. 2G, 500M)'
+    required: false
+    default: '2G'
+  github-token:
+    description: 'GitHub token for downloading sccache from GitHub releases'
+    required: false
+    default: ''
+
+outputs:
+  rust-version:
+    description: 'Installed Rust version'
+    value: ${{ steps.rust-setup.outputs.version }}
+
+runs:
+  using: composite
+  steps:
+    - name: Detect runner OS
+      id: runner-os
+      uses: ./.forgejo/actions/detect-runner-os
+
+    - name: Configure Cargo environment
+      shell: bash
+      run: |
+        # Use workspace-relative paths for better control and consistency
+        echo "CARGO_HOME=${{ github.workspace }}/.cargo" >> $GITHUB_ENV
+        echo "CARGO_TARGET_DIR=${{ github.workspace }}/target" >> $GITHUB_ENV
+        echo "SCCACHE_DIR=${{ github.workspace }}/.sccache" >> $GITHUB_ENV
+        echo "RUSTUP_HOME=${{ github.workspace }}/.rustup" >> $GITHUB_ENV
+
+        # Limit binstall resolution timeout to avoid GitHub rate limit delays
+        echo "BINSTALL_MAXIMUM_RESOLUTION_TIMEOUT=10" >> $GITHUB_ENV
+
+        # Ensure directories exist for first run
+        mkdir -p "${{ github.workspace }}/.cargo"
+        mkdir -p "${{ github.workspace }}/.sccache"
+        mkdir -p "${{ github.workspace }}/target"
+        mkdir -p "${{ github.workspace }}/.rustup"
+
+    - name: Start cache restore group
+      shell: bash
+      run: echo "::group::📦 Restoring caches (registry, toolchain, build artifacts)"
+
+    - name: Cache Cargo registry and git
+      id: registry-cache
+      uses: https://github.com/actions/cache@v4
+      with:
+        path: |
+          .cargo/registry/index
+          .cargo/registry/cache
+          .cargo/git/db
+        # Registry cache saved per workflow, restored from any workflow's cache
+        # Each workflow maintains its own registry that accumulates its needed crates
+        key: cargo-registry-${{ steps.runner-os.outputs.slug }}-${{ github.workflow }}
+        restore-keys: |
+          cargo-registry-${{ steps.runner-os.outputs.slug }}-
+
+    - name: Cache toolchain binaries
+      id: toolchain-cache
+      uses: https://github.com/actions/cache@v4
+      with:
+        path: |
+          .cargo/bin
+          .rustup/toolchains
+          .rustup/update-hashes
+        # Shared toolchain cache across all Rust versions
+        key: toolchain-${{ steps.runner-os.outputs.slug }}
+
+    - name: Debug GitHub token availability
+      shell: bash
+      run: |
+        if [ -z "${{ inputs.github-token }}" ]; then
+          echo "⚠️ No GitHub token provided - sccache will use fallback download method"
+        else
+          echo "✅ GitHub token provided for sccache"
+        fi
+
+    - name: Setup sccache
+      uses: https://github.com/mozilla-actions/sccache-action@v0.0.9
+      with:
+        token: ${{ inputs.github-token }}
+
+    - name: Cache build artifacts
+      id: build-cache
+      uses: https://github.com/actions/cache@v4
+      with:
+        path: |
+          target/**/deps
+          !target/**/deps/*.rlib
+          target/**/build
+          target/**/.fingerprint
+          target/**/incremental
+          target/**/*.d
+          /timelord/
+        # Build artifacts - cache per code change, restore from deps when code changes
+        key: >-
+          build-${{ steps.runner-os.outputs.slug }}-${{ inputs.rust-version }}${{ inputs.cache-key-suffix && format('-{0}', inputs.cache-key-suffix) || '' }}-${{ hashFiles('rust-toolchain.toml', '**/Cargo.lock') }}-${{ hashFiles('**/*.rs', '**/Cargo.toml') }}
+        restore-keys: |
+          build-${{ steps.runner-os.outputs.slug }}-${{ inputs.rust-version }}${{ inputs.cache-key-suffix && format('-{0}', inputs.cache-key-suffix) || '' }}-${{ hashFiles('rust-toolchain.toml', '**/Cargo.lock') }}-
+
+    - name: End cache restore group
+      shell: bash
+      run: echo "::endgroup::"
+
+    - name: Setup Rust toolchain
+      shell: bash
+      run: |
+        # Install rustup if not already cached
+        if ! command -v rustup &> /dev/null; then
+          echo "::group::📦 Installing rustup"
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --no-modify-path --default-toolchain none
+          source "$CARGO_HOME/env"
+          echo "::endgroup::"
+        else
+          echo "✅ rustup already available"
+        fi
+
+        # Setup the appropriate Rust version
+        if [[ -n "${{ inputs.rust-version }}" ]]; then
+          echo "::group::📦 Setting up Rust ${{ inputs.rust-version }}"
+          # Set override first to prevent rust-toolchain.toml from auto-installing
+          rustup override set ${{ inputs.rust-version }} 2>/dev/null || true
+
+          # Check if we need to install/update the toolchain
+          if rustup toolchain list | grep -q "^${{ inputs.rust-version }}-"; then
+            rustup update ${{ inputs.rust-version }}
+          else
+            rustup toolchain install ${{ inputs.rust-version }} --profile minimal -c cargo,clippy,rustfmt
+          fi
+        else
+          echo "::group::📦 Setting up Rust from rust-toolchain.toml"
+          rustup show
+        fi
+        echo "::endgroup::"
+
+    - name: Configure PATH and install tools
+      shell: bash
+      env:
+        GITHUB_TOKEN: ${{ inputs.github-token }}
+      run: |
+        # Add .cargo/bin to PATH permanently for all subsequent steps
+        echo "${{ github.workspace }}/.cargo/bin" >> $GITHUB_PATH
+
+        # For this step only, we need to add it to PATH since GITHUB_PATH takes effect in the next step
+        export PATH="${{ github.workspace }}/.cargo/bin:$PATH"
+
+        # Install cargo-binstall for fast binary installations
+        if command -v cargo-binstall &> /dev/null; then
+          echo "✅ cargo-binstall already available"
+        else
+          echo "::group::📦 Installing cargo-binstall"
+          curl -L --proto '=https' --tlsv1.2 -sSf https://raw.githubusercontent.com/cargo-bins/cargo-binstall/main/install-from-binstall-release.sh | bash
+          echo "::endgroup::"
+        fi
+
+        if command -v prek &> /dev/null; then
+          echo "✅ prek already available"
+        else
+          echo "::group::📦 Installing prek"
+          # prek isn't regularly published to crates.io, so we use git source
+          cargo-binstall -y --no-symlinks --git https://github.com/j178/prek prek
+          echo "::endgroup::"
+        fi
+
+        if command -v timelord &> /dev/null; then
+          echo "✅ timelord already available"
+        else
+          echo "::group::📦 Installing timelord"
+          cargo-binstall -y --no-symlinks timelord-cli
+          echo "::endgroup::"
+        fi
+
+    - name: Configure sccache environment
+      shell: bash
+      run: |
+        echo "RUSTC_WRAPPER=sccache" >> $GITHUB_ENV
+        echo "CMAKE_C_COMPILER_LAUNCHER=sccache" >> $GITHUB_ENV
+        echo "CMAKE_CXX_COMPILER_LAUNCHER=sccache" >> $GITHUB_ENV
+        echo "CMAKE_CUDA_COMPILER_LAUNCHER=sccache" >> $GITHUB_ENV
+        echo "SCCACHE_GHA_ENABLED=true" >> $GITHUB_ENV
+
+        # Configure incremental compilation GC
+        # If we restored from old cache (partial hit), clean up aggressively
+        if [[ "${{ steps.build-cache.outputs.cache-hit }}" != "true" ]]; then
+          echo "♻️ Partial cache hit - enabling cache cleanup"
+          echo "CARGO_INCREMENTAL_GC_THRESHOLD=5" >> $GITHUB_ENV
+        fi
+
+    - name: Install Rust components
+      if: inputs.rust-components != ''
+      shell: bash
+      run: |
+        echo "📦 Installing components: ${{ inputs.rust-components }}"
+        rustup component add ${{ inputs.rust-components }}
+
+    - name: Install Rust target
+      if: inputs.rust-target != ''
+      shell: bash
+      run: |
+        echo "📦 Installing target: ${{ inputs.rust-target }}"
+        rustup target add ${{ inputs.rust-target }}
+
+    - name: Output version and summary
+      id: rust-setup
+      shell: bash
+      run: |
+        RUST_VERSION=$(rustc --version | cut -d' ' -f2)
+        echo "version=$RUST_VERSION" >> $GITHUB_OUTPUT
+
+        echo "📋 Setup complete:"
+        echo "  Rust: $(rustc --version)"
+        echo "  Cargo: $(cargo --version)"
+        echo "  prek: $(prek --version 2>/dev/null || echo 'installed')"
+        echo "  timelord: $(timelord --version 2>/dev/null || echo 'installed')"