docs: document the Claude Code CI workflows

[GEM-312]

Adds a short README under .github/workflows/ describing the two Claude Code
workflows (mention bot + auto PR review) and the Linux-runner build caveat.

Also serves as the first live test of the claude-review.yml auto-review
workflow now that it's on main.

🤖 Generated with Claude Code

[claude]

Reviewed against CLAUDE.md. The diff is clean — it's a single documentation file (.github/workflows/README.md) with no Swift code, so the §1–§5 Architecture Rules don't apply here.

I verified the README's claims against the actual workflow files and they're all accurate:

• Both workflows require the ANTHROPIC_API_KEY secret ✓
• claude.yml triggers on @claude mentions (comment, review, issue body/title) ✓
• claude-review.yml runs on opened/updated PRs (opened, synchronize) with contents: read (read-only) ✓
• Both run on ubuntu-latest, so the Linux/no-Xcode-build caveat is correct ✓

Nothing to flag. 🤖 Generated with Claude Code

[GEM-312]

Reviewed against CLAUDE.md. The diff is clean — it's a single documentation file (.github/workflows/README.md) with no Swift code, so the §1–§5 Architecture Rules don't apply here.

I verified the README's claims against the actual workflow files and they're all accurate:

• Both workflows require the ANTHROPIC_API_KEY secret ✓
• claude.yml triggers on @claude mentions (comment, review, issue body/title) ✓
• claude-review.yml runs on opened/updated PRs (opened, synchronize) with contents: read (read-only) ✓
• Both run on ubuntu-latest, so the Linux/no-Xcode-build caveat is correct ✓

Nothing to flag. 🤖 Generated with Claude Code

workflow is set

[GEM-312]

@claude anthropic key is set

[claude]

Claude finished @GEM-312's task in 14s —— View job

---

👍 Confirmed — the auto-review workflow is live

Thanks, GEM! This PR has now successfully exercised both Claude Code workflows on main:

• claude-review.yml — auto-fired on PR open and posted the review you see above (the README claim-verification comment).
• claude.yml — responding right now to your @claude mention. ✅

No further action needed on the docs themselves — the .github/workflows/README.md content was already verified accurate against the live workflow files in the earlier review. The PR is good to merge whenever you're ready.
· test-claude-auto-review

[GEM-312]

@claude great we are all set then!

[claude]

Claude finished @GEM-312's task in 11s —— View job

---

🎉 All set!

Both Claude Code workflows are confirmed live on main, and the .github/workflows/README.md docs were already verified accurate against the workflow files. Nothing left to do here — this PR is good to merge whenever you're ready.

Thanks, GEM! 👋
· test-claude-auto-review