chore: add llvm-cov to CI

.github/workflows/coverage.yml

@@ -0,0 +1,63 @@
+name: Coverage
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["**"]
+
+jobs:
+  coverage:
+    runs-on: 
+      - runs-on=${{ github.run_id }}
+      - runner=64cpu-linux-arm64
+      - tag=coverage
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install Rust toolchain (nightly)
+        uses: dtolnay/rust-toolchain@nightly
+
+      - name: Install llvm-tools-preview component
+        run: rustup component add llvm-tools-preview --toolchain nightly      
+
+      - uses: Swatinem/rust-cache@v2
+        with:
+          cache-on-failure: true        
+
+      - name: Install cargo-llvm-cov
+        run: cargo install cargo-llvm-cov          
+
+      - name: Run coverage
+        run: RUST_MIN_STACK=8388608 AXIOM_FAST_TEST=1 cargo llvm-cov --json --output-path=coverage --jobs $(nproc) --profile=fast --features parallel --ignore-filename-regex 'tests|examples' --no-report
+
+      - name: Generate report
+        run: cargo llvm-cov --json --output-path coverage/
+
+      - name: Parse detailed coverage report
+        id: parse
+        run: |
+          # Initialize the markdown table header
+          echo "| File               | Coverage | Total Lines | Covered Lines |" > coverage_table.md
+          echo "|--------------------|----------|-------------|---------------|" >> coverage_table.md
+
+          # Parse each file's data and append it to the table
+          jq -r '.files[] | "| \(.file) | \(.coverage.lines.percent)% | \(.coverage.lines.total) | \(.coverage.lines.covered) |"' coverage.json >> coverage_table.md
+
+      - name: Set markdown table as output
+        id: table_output
+        run: echo "table=$(< coverage_table.md)" >> $GITHUB_ENV
+
+      - name: Post detailed coverage results as PR comment
+        uses: actions/github-script@v6
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const table = process.env.table;
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: `### Detailed Coverage Report\n\n${table.replace(/\|/g, '\\|')}`
+            });