ci: release pull requests, and conventional-commit PR titles (#1)

Releases as pull requests, the same in all five app repos (hub, catalog, live, riftbound, karaoke). The Gitea side (PRs only into main, squash merges, required checks, `v*` tags only by release-bot, its `RELEASE_TOKEN` org secret) is dhkatz/infra `modules/app-repo`.

- **`.gitea/workflows/pull-request.yml`**: the PR title must be a conventional commit (`feat(api): …`, `fix: …`, `feat!: …`); it becomes the commit on main. `chore(release)` only from release-bot's `release` branch. Required to merge (`Pull request / title`).
- **`.gitea/default_merge_message/SQUASH_TEMPLATE.md`**: the squash commit is `<PR title> (#<n>)` plus the description.
- **`.gitea/workflows/release.yml`**, on every push to main, as release-bot (`RELEASE_TOKEN`):
  - if the commit is a merged `chore(release): vX.Y.Z`: tag it vX.Y.Z (lightweight), push the tag (CI builds the image, Komodo deploys prod), publish the release with git-cliff's notes;
  - otherwise, if anything releasable landed since the last tag: rewrite the `release` branch (CHANGELOG.md) and open or update `chore(release): vX.Y.Z`.
- **`cliff.toml`** (git-cliff 2.14.2, pinned by sha512): feat → minor, fix/perf/revert → patch, breaking → minor while 0.x; chore/ci/docs/test/style/build/refactor alone don't release. Only conventional commits count, so the history before this is left out.
- **`CHANGELOG.md`**: header only; release PRs fill it.
- Agent notes (CLAUDE.md / AGENTS.md): the PR flow and title format; never tag by hand.

After merging, `Release` runs on main and should report nothing to release (this PR is `ci:`); the first `feat:`/`fix:` PR merged after it opens the first release PR.

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Reviewed-on: #1
Co-authored-by: dhkatz <[email protected]>

.gitea/default_merge_message/SQUASH_TEMPLATE.md

@@ -0,0 +1,3 @@
+${PullRequestTitle} (#${PullRequestIndex})
+
+${PullRequestDescription}