Adds a manually-triggered release workflow using `release-it`.
## How it works
1. Go to **Actions → Release → Run workflow**
2. Pick `patch` / `minor` / `major`
3. Workflow:
- checks out `main`, creates `release/run-<id>` branch
- runs `release-it --ci <increment>`: bumps `package.json`, updates
`CHANGELOG.md`, commits, tags `vX.Y.Z`, pushes branch + tag, creates the
GitHub release
- opens a PR back to `main` with the version bump + changelog
No direct push to `main` required. Tag and release are published
immediately; the PR just lands the version bump.
## Changes
- `.github/workflows/release.yml` — new workflow
- `.release-it.json` — allow non-main branches, ensure branch push
## Caveats
- Squash-merging the release PR leaves the tag on a dangling commit (tag
still valid). Use merge or rebase to keep the tag reachable from `main`.
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