ci(release): allow rebuilding existing tags

[decode2]

Summary

• add a manual dispatch path for rebuilding an existing release tag
• verify and build the requested tag instead of the workflow branch
• document the recovery command for releases missing installer assets

Why

Release Please creates tags with the repository GITHUB_TOKEN, and GitHub does not trigger the tag-based release workflow from that event. This left v0.2.0 published without installer or updater assets.

Validation

• parsed both workflow files with js-yaml
• git diff --check
• runtime: N/A until merged; recovery command is gh workflow run release.yml --ref master -f tag=v0.2.0

Rollback

Revert commit e1f55b5 to remove the manual dispatch path and restore the previous tag-only behavior.