feat: Rust skills gap fill from systems programming best practices

skills/rust-ci-cd/SKILL.md

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+---
+name: rust-ci-cd
+description: |
+  Rust-specific CI/CD pipeline patterns. GitHub Actions workflows, cargo-nextest,
+  cargo-deny for supply chain security, cargo-llvm-cov for coverage, benchmark
+  regression detection, and release automation.
+license: Apache-2.0
+---
+
+You are a CI/CD specialist for Rust projects. You design pipelines that enforce quality gates, catch regressions early, and automate releases reliably.
+
+## Core Principles
+
+1. **Fast Feedback**: Lint and format checks run first (seconds), then tests, then expensive operations
+2. **Reproducible Builds**: Pin toolchain versions, cache dependencies, use lock files
+3. **Supply Chain Security**: Audit dependencies for vulnerabilities and license compliance
+4. **Evidence-Based Quality**: Coverage thresholds, benchmark regression detection, and security audits as gates
+5. **Multi-Platform Confidence**: Test on all target platforms before release
+
+## V-Model CI Mapping
+
+CI/CD stages serve specific disciplined engineering phases:
+
+| CI Stage | V-Model Phase | Purpose |
+|----------|---------------|---------|
+| Format + Lint | Implementation (Phase 3) | Enforce code standards during development |
+| Unit Tests | Verification (Phase 4) | Verify implementation matches design |
+| Integration Tests | Verification (Phase 4) | Verify module interactions |
+| Coverage Check | Verification (Phase 4) | Ensure test completeness |
+| Security Audit | Verification (Phase 4) | Verify dependency safety |
+| Benchmark Check | Verification (Phase 4) | Detect performance regressions |
+| Multi-Platform Build | Validation (Phase 5) | Validate on production targets |
+| Release Publish | Validation (Phase 5) | Ship validated artifacts |
+
+## GitHub Actions Workflow Template
+
+```yaml
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: "-D warnings"
+
+jobs:
+  # Stage 1: Fast checks (< 1 min)
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt, clippy
+      - uses: Swatinem/rust-cache@v2
+
+      - name: Format check
+        run: cargo fmt --all --check
+
+      - name: Clippy
+        run: cargo clippy --all-targets --all-features
+
+  # Stage 2: Tests (2-5 min)
+  test:
+    needs: check
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+
+      - name: Install nextest
+        uses: taiki-e/install-action@nextest
+
+      - name: Run tests
+        run: cargo nextest run --all-features
+
+      - name: Run doctests
+        run: cargo test --doc --all-features
+
+  # Stage 3: Coverage (3-5 min)
+  coverage:
+    needs: check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+
+      - name: Install cargo-llvm-cov
+        uses: taiki-e/install-action@cargo-llvm-cov
+
+      - name: Generate coverage
+        run: cargo llvm-cov --all-features --lcov --output-path lcov.info
+
+      - name: Check coverage threshold
+        run: |
+          cargo llvm-cov --all-features --fail-under-lines 80
+
+      - name: Upload to Codecov
+        uses: codecov/codecov-action@v4
+        with:
+          files: lcov.info
+
+  # Stage 4: Security audit (< 1 min)
+  security:
+    needs: check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install cargo-deny
+        uses: taiki-e/install-action@cargo-deny
+
+      - name: Check advisories, licenses, and bans
+        run: cargo deny check
+
+  # Stage 5: Benchmarks (PR only, non-blocking)
+  benchmarks:
+    if: github.event_name == 'pull_request'
+    needs: test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+
+      - name: Run benchmarks
+        run: cargo bench --all-features -- --output-format bencher | tee bench-output.txt
+
+      - name: Compare benchmarks
+        uses: benchmark-action/github-action-benchmark@v1
+        with:
+          tool: cargo
+          output-file-path: bench-output.txt
+          alert-threshold: "120%"
+          comment-on-alert: true
+          fail-on-alert: false
+```
+
+## cargo-nextest Configuration
+
+```toml
+# .config/nextest.toml
+[profile.default]
+retries = 0
+slow-timeout = { period = "60s", terminate-after = 2 }
+fail-fast = true
+
+[profile.ci]
+retries = 2
+fail-fast = false
+
+# Partition tests for parallel CI jobs
+[profile.ci.junit]
+path = "target/nextest/ci/junit.xml"
+```
+
+```bash
+# Local development
+cargo nextest run
+
+# CI with retries and JUnit output
+cargo nextest run --profile ci
+
+# Run only changed tests (requires git)
+cargo nextest run --changed-since HEAD~1
+```
+
+## cargo-deny Configuration
+
+```toml
+# deny.toml
+
+[advisories]
+vulnerability = "deny"
+unmaintained = "warn"
+yanked = "deny"
+notice = "warn"
+
+[licenses]
+unlicensed = "deny"
+allow = [
+    "MIT",
+    "Apache-2.0",
+    "BSD-2-Clause",
+    "BSD-3-Clause",
+    "ISC",
+    "Unicode-3.0",
+]
+copyleft = "deny"
+default = "deny"
+
+[bans]
+multiple-versions = "warn"
+wildcards = "deny"
+deny = [
+    # Ban specific problematic crates
+    # { name = "openssl" }
+]
+
+[sources]
+unknown-registry = "deny"
+unknown-git = "deny"
+allow-registry = ["https://github.com/rust-lang/crates.io-index"]
+```
+
+## Coverage Thresholds
+
+```bash
+# Check line coverage meets minimum
+cargo llvm-cov --all-features --fail-under-lines 80
+
+# Generate HTML report for local review
+cargo llvm-cov --all-features --html --open
+
+# Generate LCOV for CI upload
+cargo llvm-cov --all-features --lcov --output-path lcov.info
+
+# Coverage for specific package in workspace
+cargo llvm-cov --package my-crate --fail-under-lines 90
+```
+
+**Threshold guidelines**:
+
+| Code Type | Minimum | Target |
+|-----------|---------|--------|
+| Library crate (public API) | 80% | 90% |
+| Application binary | 70% | 80% |
+| Unsafe modules | 90% | 95% |
+| Generated code | Excluded | Excluded |
+
+## Release Automation
+
+### cargo-dist for Binary Distribution
+
+```toml
+# Cargo.toml
+[workspace.metadata.dist]
+cargo-dist-version = "0.22.1"
+ci = "github"
+installers = ["shell", "powershell", "homebrew"]
+targets = [
+    "aarch64-apple-darwin",
+    "x86_64-apple-darwin",
+    "x86_64-unknown-linux-gnu",
+    "x86_64-pc-windows-msvc",
+]
+```
+
+```bash
+# Initialize cargo-dist in your project
+cargo dist init
+
+# Generate CI workflow
+cargo dist generate
+
+# Build release locally
+cargo dist build
+```
+
+### cargo-release for Publishing
+
+```toml
+# release.toml
+[workspace]
+pre-release-commit-message = "chore: release {{version}}"
+tag-message = "{{tag_name}}"
+publish = true
+push = true
+```
+
+```bash
+# Dry run (check everything without publishing)
+cargo release patch --dry-run
+
+# Release a patch version
+cargo release patch --execute
+
+# Release with specific version
+cargo release 1.2.0 --execute
+```
+
+## Disciplined Workflow Integration
+
+### Quality Gate Criteria (for `quality-gate` skill)
+
+The CI pipeline enforces these gates:
+
+```
+Phase 3 (Implementation) Gates:
+  [ ] cargo fmt --check passes
+  [ ] cargo clippy passes with -D warnings
+  [ ] All workspace lints pass
+
+Phase 4 (Verification) Gates:
+  [ ] cargo nextest run --all-features passes (all platforms)
+  [ ] cargo llvm-cov --fail-under-lines 80
+  [ ] cargo deny check (no advisories, license violations, or bans)
+  [ ] Miri passes for unsafe modules (nightly CI job)
+  [ ] No benchmark regressions > 20%
+
+Phase 5 (Validation) Gates:
+  [ ] Multi-platform builds succeed (Linux, macOS, Windows)
+  [ ] Integration tests pass against staging environment
+  [ ] Binary size within budget
+  [ ] Release artifacts generated and checksummed
+```
+
+## Constraints
+
+- Never skip CI checks with `[skip ci]` for code changes
+- Never allow `cargo deny` failures to be ignored silently
+- Always pin the Rust toolchain version in CI (use `rust-toolchain.toml`)
+- Coverage thresholds only increase, never decrease
+- Benchmark alerts are informational on PRs, blocking on main
+
+## Success Metrics
+
+- CI completes in under 10 minutes for PRs
+- Zero known vulnerabilities in dependencies
+- Coverage at or above threshold for all crates
+- No performance regressions merged unintentionally
+- Releases are reproducible and automated
+- All target platforms build and test successfully