fix: overhaul release pipeline — 5 issues resolved

1. version input now optional — auto-increment from release_type works
2. replaced deprecated actions/create-release@v1 with gh release create
3. race condition fixed — release commit uses [skip ci], removed fragile
   github.actor guard from build-and-push.yaml
4. simplified gh-pages publishing — uses clean temp dir + shallow clone
   instead of convoluted git worktree fallback
5. version parsing strips pre-release suffixes (e.g., 2.0.0-dev → 2.0.0)

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

.github/workflows/build-and-push.yaml

@@ -16,9 +16,6 @@ env:
 jobs:
   build-and-push:
     runs-on: ubuntu-latest
-    # Skip builds triggered by release-unified.yaml commits (github-actions[bot])
-    # to prevent racing with the release workflow's own Docker build
-    if: github.event_name == 'workflow_dispatch' || github.event_name == 'pull_request' || github.actor != 'github-actions[bot]'
     permissions:
       contents: read
       packages: write