feat: rust-ci-cd skill -- Rust-specific CI/CD pipeline patterns

[AlexMikhalev]

Parent Epic: #62

What

New skill: rust-ci-cd covering Rust-specific continuous integration and delivery patterns.

Skill Content

1. GitHub Actions Workflow Template -- Multi-platform matrix (Linux, macOS, Windows), caching, cargo-nextest
2. Linting and Formatting -- cargo fmt --check, clippy with RUSTFLAGS, workspace-level lints
3. Security Auditing -- cargo deny (licenses, advisories, bans), cargo audit (rustsec), supply chain review
4. Code Coverage -- cargo-llvm-cov with codecov/coveralls integration, threshold enforcement
5. Benchmark CI -- Criterion benchmarks in CI with regression detection, bencher or criterion-compare
6. Release Automation -- cargo-dist, cargo-release, cross-compiled artifacts, checksums

Source Reference

Section 12 (CI/CD Pipeline for Rust) from RUST_SYSTEM_PROGRAMMING_BEST_PRACTICES.md

Disciplined Engineering Alignment

This skill is a cross-cutting enabler for all disciplined phases:

Phase	Skill	CI/CD Relevance
Research	disciplined-research	Audit existing CI pipeline gaps; identify missing gates (coverage, security, benchmarks)
Design	disciplined-design	Specify CI pipeline stages; define quality gates and their thresholds
Implementation	disciplined-implementation	Each CI stage = one step; cargo-nextest first, then coverage, then security audit, then benchmarks
Verification	disciplined-verification	CI IS verification infrastructure: coverage thresholds, lint gates, Miri/sanitizer integration
Validation	disciplined-validation	CI validates release readiness: multi-platform builds pass, security audit clean, benchmarks stable

Key integration point: The quality-gate skill should reference rust-ci-cd for Rust-specific gate criteria.

The SKILL.md should include:

• A "V-Model CI Mapping" section showing which CI stages serve which disciplined phase
• Gate criteria tables compatible with quality-gate skill format

Why a New Skill (Not Extension)

CI/CD cuts across all Rust skills (development, performance, testing). It's a distinct operational concern with its own toolchain and patterns.

Acceptance Criteria

• skills/rust-ci-cd/SKILL.md created with full content
• Includes ready-to-use GitHub Actions YAML templates
• Covers cargo-deny configuration example
• Covers cargo-llvm-cov threshold setup
• V-Model CI mapping section included
• Cross-references quality-gate skill