ci: add release as valid PR label

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: frantic1048

.github/workflows/pr-labels.yml

@@ -16,5 +16,6 @@ jobs:
           github-token: '${{ secrets.GITHUB_TOKEN }}'
           valid-labels: >-
             breaking-change, bugfix, documentation, enhancement,
-            refactor, performance, new-feature, maintenance, ci, dependencies
+            refactor, performance, new-feature, maintenance, ci, dependencies,
+            release
           disable-reviews: true