docs: add commit rules section to CLAUDE.md

CLAUDE.md

@@ -501,6 +501,25 @@ BODY:
 - PRs require all CI checks to pass before merging.
 - Never commit directly to `main`.
 
+### Commit Rules (enforced by AI)
+
+These rules apply to every commit made during AI-assisted implementation:
+
+| Rule | Detail |
+|------|--------|
+| **Two commits per TDD step** | 1st commit = failing tests (Red), 2nd commit = passing implementation (Green) |
+| **Commit after each step** | Never accumulate multiple steps in one commit |
+| **Red commit subject** | `test(<scope>): add failing tests for step <N> — <short description>` |
+| **Green commit subject** | `feat(<scope>): implement step <N> — <short description>` |
+| **Scope values** | `backend`, `frontend`, `docker`, `ci`, `config` |
+| **Body** | Optional but encouraged: list what was added/changed |
+| **No `--no-verify`** | Never bypass git hooks |
+| **No force push** | Never use `--force` on shared branches |
+| **Atomic commits** | Each commit must leave the build green (except deliberate Red-phase test commits) |
+| **`chore` for housekeeping** | Config changes, dependency tweaks, file renames → `chore(<scope>):` |
+| **`fix` for bug fixes** | `fix(<scope>): <what was broken and how it was fixed>` |
+| **`docs` for documentation** | Changes to `CLAUDE.md`, `INSTRUCTIONS.md`, `README.md` → `docs:` |
+
 ### GitHub Actions Workflows
 
 | Workflow file              | Trigger                    | What it does                                              |