fix: do not fail the release when pyproject.toml is already current

The release step added in #17 commits the computed version unconditionally. If
pyproject.toml already carries that version -- a re-run of a release, or a
version corrected by hand -- there is nothing staged and `git commit` exits
non-zero, failing the job after the image has already been pushed and before
the tag is created.

Skip the commit and its push in that case, and tag either way.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-and-publish.yaml

@@ -188,11 +188,19 @@ jobs:
           git config user.name "${{ github.actor }}"
           git config user.email "${{ github.actor }}@users.noreply.${REGISTRY}"
           git add pyproject.toml
-          git commit -m "chore(release): v${VERSION}"
 
+          # The file may already carry this version, in which case there is
+          # nothing to commit and `git commit` would fail the job after the
+          # image has already been pushed.
+          if git diff --cached --quiet; then
+            echo "pyproject.toml is already at ${VERSION}"
+          else
+            git commit -m "chore(release): v${VERSION}"
             # Push the branch before the tag. If main has moved on and this push
             # is rejected, the job fails without having left a tag pointing at a
             # commit that is not on main.
             git push origin "HEAD:${GITHUB_REF_NAME}"
+          fi
+
           git tag -a "v${VERSION}" -m "v${VERSION}"
           git push origin "v${VERSION}"