[add] pipeline for generating code coverage on pull requests.

Author: vmarcella

.github/workflows/coverage.yml

@@ -0,0 +1,106 @@
+name: Code Coverage
+
+on:
+  pull_request:
+    branches: [main]
+
+  push:
+    branches: [main]
+
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pull-requests: write
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  coverage:
+    name: Generate code coverage with cargo-llvm-cov
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v4
+
+      - name: Cache cargo builds
+        uses: Swatinem/rust-cache@v2
+
+      - name: Install Rust toolchain with llvm-tools-preview
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          components: llvm-tools-preview
+
+      - name: Install cargo-llvm-cov
+        uses: taiki-e/install-action@cargo-llvm-cov
+
+      - name: Install Linux deps for winit/wgpu
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y \
+            pkg-config libx11-dev libxcb1-dev libxcb-render0-dev \
+            libxcb-shape0-dev libxcb-xfixes0-dev libxkbcommon-dev \
+            libwayland-dev libudev-dev \
+            libvulkan-dev libvulkan1 mesa-vulkan-drivers vulkan-tools
+
+      - name: Install Linux deps for audio
+        run: |
+          sudo apt-get install -y libasound2-dev
+
+      - name: Configure Vulkan (Ubuntu)
+        run: |
+          echo "WGPU_BACKEND=vulkan" >> "$GITHUB_ENV"
+          # Prefer Mesa's software Vulkan (lavapipe) for headless availability
+          echo "VK_ICD_FILENAMES=/usr/share/vulkan/icd.d/lvp_icd.x86_64.json" >> "$GITHUB_ENV"
+          vulkaninfo --summary || true
+
+      - name: Generate coverage JSON (summary only)
+        run: |
+          cargo llvm-cov --workspace \
+            --features lambda-rs/with-vulkan,lambda-rs/audio-output-device \
+            --json --summary-only \
+            --output-path coverage.json
+
+      - name: Extract total line coverage percentage
+        id: cov
+        run: |
+          pct=$(jq -r '(.data[0].totals.lines.percent // 0)' coverage.json)
+          covered=$(jq -r '(.data[0].totals.lines.covered // 0)' coverage.json)
+          total=$(jq -r '(.data[0].totals.lines.count // 0)' coverage.json)
+          echo "pct=$pct" >> "$GITHUB_OUTPUT"
+          echo "covered=$covered" >> "$GITHUB_OUTPUT"
+          echo "total=$total" >> "$GITHUB_OUTPUT"
+
+      - name: Comment on PR
+        if: github.event_name == 'pull_request'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const pct = `${{ steps.cov.outputs.pct }}`;
+            const covered = `${{ steps.cov.outputs.covered }}`;
+            const total = `${{ steps.cov.outputs.total }}`;
+
+            const body = [
+              '### ✅ Coverage Report',
+              '',
+              '| Metric | Value |',
+              '|--------|-------|',
+              `| **Total Line Coverage** | ${pct}% |`,
+              `| **Lines Covered** | ${covered} / ${total} |`,
+              '',
+              '*Generated by [cargo-llvm-cov](https://github.com/taiki-e/cargo-llvm-cov)*'
+            ].join('\n');
+
+            const { owner, repo } = context.repo;
+            const issue_number = context.issue.number;
+            await github.rest.issues.createComment({ owner, repo, issue_number, body });
+
+      - name: Upload coverage JSON as artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-report
+          path: coverage.json
+          retention-days: 30