ci: split monolithic CI into parallel jobs

[Bisht13]

Summary

• Splits the single build_and_test CI job into separate parallel jobs: fmt, clippy, build+test, and documentation — matching the upstream whir CI pattern
• Lightweight checks (fmt, typos, unused deps) no longer wait behind a full build, giving faster feedback on failures
• All provekit-specific settings preserved (ARM runner, nightly-2026-03-04 toolchain, moonrepo/setup-rust, concurrency groups, doc tests)

Jobs

Job	Runner	Purpose
build_and_test	ubuntu-24.04-arm	Build + unit/integration tests + doc tests
cargo_clippy	ubuntu-24.04-arm	Lint check with all features
cargo_fmt	ubuntu-24.04-arm	Format check
cargo_doc	ubuntu-24.04-arm	Documentation build with -D warnings
unused_deps	ubuntu-latest	cargo-machete unused dependency check
typos	ubuntu-latest	Spell check

Test plan

• Verify all 6 jobs run in parallel on a PR
• Confirm fmt/clippy/typos fail fast without waiting for build
• Validate concurrency cancellation still works on updated pushes

[Bisht13]

/claude-review

[github-actions]

Code Review

Summary

This PR refactors the monolithic build_and_test CI job into six focused parallel jobs (build_and_test, cargo_clippy, cargo_fmt, cargo_doc, unused_deps, typos). It also adds --with-metadata to cargo-machete and [package.metadata.cargo-machete] ignore sections to suppress false positives for build-script and proc-macro dependencies.

Review

Correctness & Soundness
No production code changes — this is CI infrastructure only. No soundness concerns.

A few correctness checks:

• RUSTDOCFLAGS: "--cfg doc_cfg -D warnings" is correctly preserved in the new cargo_doc job. ✓
• components: rustfmt / components: clippy are properly scoped to only the jobs that need them. ✓
• Workflow-level concurrency group (${{ github.workflow }}-${{ github.ref }}) still governs all jobs, so push-cancellation continues to work correctly. ✓
• --with-metadata on cargo-machete is an additive improvement — enables dep graph analysis so build-script and macro deps are better detected before the manual ignores even fire.

Code Quality

• The three [package.metadata.cargo-machete] ignore entries each carry a clear comment explaining why the dep is suppressed (build.rs, proc-macro expansion). Good.
• Job names are consistent and descriptive.
• Minor nit (non-blocking): cargo_fmt runs on ubuntu-24.04-arm but rustfmt output is entirely platform-independent. Switching it (and potentially cargo_clippy/cargo_doc) to ubuntu-latest would free up the ARM slot for the heavier build_and_test job and potentially speed up queue time. That said, using a consistent runner tier is also a defensible choice.
• Minor nit (non-blocking): cargo clippy does not pass -- -D warnings, so clippy warnings won't fail CI. This matches the previous behaviour and the CLAUDE.md command reference, so it's not a regression — but it's worth noting if stricter lint enforcement is desired in the future.

Testing
CI-only change. The PR description confirms all six jobs ran in parallel and fmt/clippy/typos failed fast. No Rust logic to test.

Suggestions

• (Non-blocking) Consider moving cargo_fmt to ubuntu-latest to reduce ARM runner load.
• (Non-blocking) If strict linting is desired, add -- -D warnings to the clippy invocation in cargo_clippy.

Verdict

✅ Approve — clean, well-motivated CI improvement with no regressions.