Release v0.6.3

[github-actions]

Publish v0.6.3 to main with all released changes and the updated package download.

Release: https://github.com/d3cker/opencode2-github-automation/releases/tag/v0.6.3

Fixed

• Generate release descriptions from the matching changelog section, so publishing
  a tag before its PR merges no longer produces notes about an earlier release.
• Show the latest published stable package's versioned download URL in the README
  on release after successful publication, then promote it to main through a PR.

Release process

• Run full CI when feature PRs target release, including new commits to open PRs.
  Ordinary feature pushes no longer run CI or build packages.
• Publish an automatic patch after a PR merges into release, and support manual
  version tags on that branch without a second version bump.
• Recover interrupted publication without moving tags or republishing completed
  packages. Commit README on release before opening or updating its PR to main.
• Keep main changes behind PR merges and verify that promotion contains the
  published package's code and updated download links.

Merge this PR with a merge commit to preserve the long-lived release branch.