fix: enable manual publish dispatch for release backfills

[kuitos]

What changed

• add workflow_dispatch to the release workflow so publish can be run manually from GitHub Actions when a backfill is needed
• extend the publish config test to keep that manual trigger covered

Why

The recent Release workflow run on main completed successfully, but semantic-release skipped publishing because the only commit since v1.6.0 was not releasable. This PR adds a real fix: change so merging it will trigger the next patch release, and it also leaves a manual publish path in place for future operational backfills.

Impact

• merging this PR should allow the repository to publish 1.6.1
• maintainers can manually dispatch the publish workflow later if a release needs to be re-run

Validation

• bun test test/publish-config.test.ts test/github-actions-ci.test.ts
• full bun test still has the pre-existing @opencode-ai/plugin resolution error in test/index.test.ts, unrelated to this PR

[github-actions]

🎉 This PR is included in version 1.6.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀