📝 Say compat is CI-only and run by hand locally

The pipeline bullet's "(push to `main` / tag)" read like a local push hook.
State plainly that `compat` has no local tier — it is not in `check`, `verify`,
`test:ci` or any hook — and is run manually with `build && test:compat`.

CONTRIBUTING.md

@@ -20,9 +20,10 @@ the rules so agents and humans don't diverge.
 
 - **Build:** `npm run build`
 - **Test:** `npm run test`, `npm run test:ci`
-- **Compat (CI-only):** `npm run test:compat` — type-check the suite + a consumer
-  fixture against the minimum supported TypeScript; needs a built `dist/` and
-  network access (`npx`)
+- **Compat (CI-only, manual locally):** `npm run test:compat` — type-check the
+  suite + a consumer fixture against the minimum supported TypeScript; needs a
+  built `dist/` and network access (`npx`). Never part of a hook or
+  `check`/`verify`
 - **Watch:** `npm run watch` - re-runs tests on file save, humans only
 - **Checks:** `npm run check`, `npm run fix`
 - **Doc tests:** `npm run create:doc-tests` — compile the `ts`-tagged fences
@@ -47,7 +48,7 @@ faster tiers catch less, slower tiers are more thorough":
 | `npm run fix`                    | manual                  | Auto-resolve fixable issues (lint, format)                                                                                                              | ~3s   |
 | `npm run maintain`               | manual / CI (advisory)  | `maintain:knip` + `maintain:outdated` (whole-project + network scans)                                                                                   | ~10s  |
 | CI build (auto)                  | on push to `main` / tag | `build` job (build + correctness + coverage + packaging) — see [.gitea/workflows/ci.yml](./.gitea/workflows/ci.yml)                                     | ~30s+ |
-| CI compat (auto)                 | on push to `main` / tag | `compat` job — `test:compat` over the built `dist/`; gates `publish` — see [compat/](./compat)                                                          | ~15s  |
+| CI compat (auto)                 | in CI only              | `compat` job — `test:compat` over the built `dist/`; never a local tier (run by hand) — see [compat/](./compat)                                         | ~15s  |
 | CI maintain (auto, non-blocking) | on push to `main`       | `npm run maintain` — reports, never fails the build                                                                                                     | ~10s  |
 | CI publish (auto)                | on tag                  | packaging checks + `publish:publint` / `publish:attw`, then the Gitea release page and `npm publish` (skipped, and the job failed, without `NPM_TOKEN`) | ~15s  |