👷 Skip main CI run for release commits

A release pushes main and then a tag pointing at the same commit, so
the branch run re-verifies the identical SHA the tag run already
verifies (and publishes). Add a cheap release-gate job that recognizes
the '🔖 Release x.y.z' commit message on main and skips the
full build/maintain jobs; tag, PR, and ordinary main pushes are
unaffected, and the gate fails open (runs CI) if it errors.

CONTRIBUTING.md

@@ -87,7 +87,7 @@ This is why every test in the suite pairs an `expectTypeOf(...)` with an `assert
 - **Branch naming:** `feature/<desc>` / `fix/<desc>` / `chore/<desc>`
 - **Starting work:** `npm run create:branch -- <prefix>/<desc>`. It refuses, without changing anything, unless the working tree is clean (untracked files included), no merge/rebase/cherry-pick is in progress, `main` matches its upstream, and `npm run test` is green on `main` — so a later failure is always attributable to your edits. The prefix is still _your_ call, inferred from the task; the script validates it rather than guessing it.
 - **Merging:** `npm run create:finish` (on the branch). It asserts the same clean-tree / no-operation / current-`main` preconditions, fast-forwards a stale `main` (a true divergence is refused), merges the branch `--no-ff`, runs `npm run verify`, and deletes the branch only after the merge is green. The push is deliberately left to `create:release`, so the merge stays local and reviewable — read the diff yourself before finishing.
-- CI runs `npm run check` + `npm run test:ci` on every push to `main` — this is the authoritative gate.
+- CI runs `npm run check` + `npm run test:ci` on every push to `main` — this is the authoritative gate. The one exception: a push headed by a release commit (`:bookmark: Release x.y.z`) skips the full `build`/`maintain` jobs, because `create:release` pushes the tag for that exact commit right after and the tag run is the authoritative one (see `release-gate` in [.gitea/workflows/ci.yml](./.gitea/workflows/ci.yml)).
 - **Releases are NOT triggered by pushes.** Only the maintainer triggers a release (see [Publishing workflow](#publishing-workflow)).
 
 ## Publishing workflow
@@ -97,4 +97,4 @@ Publishing is CI-only by policy. Local `npm publish` is not supported. The maint
 1. All intended changes are merged to `main` and passing CI.
 2. The maintainer runs `npm run create:release`. VS Code opens `CHANGELOG.md` to finalize the `[Unreleased]` notes; because pubv refuses a dirty tree, any edit is committed first (then folded into the release commit), and pubv's interactive prompt suggests a version from those notes — the maintainer confirms or edits it.
 3. `scripts/release.sh` creates a single release commit (graduated changelog + package.json bump, amended into one commit), tags it, and pushes everything to Gitea.
-4. CI runs on the push (the `build` and `maintain` jobs); the `publish` job then fires on the tag, consuming the `dist/` artifact the `build` job produced. The job graph lives in [.gitea/workflows/ci.yml](./.gitea/workflows/ci.yml) — keep that file, not this list, as the source of truth. The publish-tier checks must pass before the artifact is published. The `publish` job also creates the Gitea release page from the matching Keep-a-Changelog section (`scripts/release-notes.sh`); it runs _before_ `npm publish` so a broken page fails CI without consuming a version, and `npm publish` stays the last step.
+4. CI fires on both pushes: the `publish` job runs on the tag (`build` + publish-tier checks + release page + `npm publish`), while the branch run's `release-gate` job recognizes the release commit and skips `build`/`maintain` — the tag verifies the identical SHA, so no work is duplicated. The job graph lives in [.gitea/workflows/ci.yml](./.gitea/workflows/ci.yml) — keep that file, not this list, as the source of truth. The publish-tier checks must pass before the artifact is published. The `publish` job also creates the Gitea release page from the matching Keep-a-Changelog section (`scripts/release-notes.sh`); it runs _before_ `npm publish` so a broken page fails CI without consuming a version, and `npm publish` stays the last step.