ci: replace manual cargo cache with Swatinem/rust-cache

[panos-xyz]

Summary

• Replace all 5 instances of manual actions/cache with Swatinem/rust-cache@v2 across build, lint, and test workflows
• Smarter cache key generation (includes Cargo.lock + Cargo.toml + toolchain version)
• Auto-cleanup of stale target artifacts prevents cache bloat
• cache-on-failure: true saves cache even on build errors for faster retries
• Reduces cache config from ~10 lines to 3 lines per job

Test plan

• Build workflow runs with cache hit/miss
• Lint workflow (clippy) runs with cache
• Test workflows (unit + doc) run with cache
• Second run on same PR shows cache restoration

[coderabbitai]

Warning

Rate limit exceeded

@panos-xyz has exceeded the limit for the number of commits that can be reviewed per hour. Please wait 5 minutes and 24 seconds before requesting another review.

Your organization is not enrolled in usage-based pricing. Contact your admin to enable usage-based pricing to continue reviews beyond the rate limit, or try again in 5 minutes and 24 seconds.

⌛ How to resolve this issue?

After the wait time has elapsed, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

We recommend that you space out your commits to avoid hitting the rate limit.

🚦 How do rate limits work?

CodeRabbit enforces hourly rate limits for each developer per organization.

Our paid plans have higher rate limits than the trial, open-source and free plans. In all cases, we re-allow further reviews after a brief timeout.

Please see our FAQ for further information.

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 8dab5742-8ee1-4919-a465-95d859a323e0

📥 Commits

Reviewing files that changed from the base of the PR and between ccbf482 and aff4d85.

📒 Files selected for processing (3)

• .github/workflows/build.yml
• .github/workflows/lint.yml
• .github/workflows/test.yml

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch panos/ci-cache

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[chengwenxi]

Code review: Approve

Clean, well-scoped CI improvement. All 4 manual actions/cache@v4 blocks are correctly replaced with Swatinem/rust-cache@v2. No cache block is missed, and the fmt job (which has no cache and doesn't need one) is correctly left untouched.

What this improves:

• Smarter cache keys (includes Cargo.toml, rustc version, job ID -- not just Cargo.lock)
• Automatic target directory cleanup prevents cache bloat
• cache-on-failure: true saves partial compilation for faster retries
• ~10 lines reduced to 3 lines per job

Verified:

• Swatinem/rust-cache is well-established (~1,770 stars, latest release v2.9.1 from 2026-03-12)
• No unrelated changes, no security concerns
• Workflow triggers, permissions, env vars, toolchain setup, and build/test commands are all untouched

[chengwenxi]

LGTM. Swatinem/rust-cache@v2 is the de facto standard — better cache keys (factors in Cargo.toml + rustc version), automatic target pruning, and cache-on-failure: true for retry perf. All 4 manual cache blocks correctly replaced.