fix: prevent stale release PR body by closing before regeneration

release-please skips updating the PR body when it finds an existing PR,
causing the changelog to miss commits that landed after the PR was
created. Fix by closing the stale PR before release-please runs so it
always creates a fresh PR with the full changelog.

Also set cancel-in-progress: true so rapid successive merges don't
race to create the PR with partial commit history.

.github/workflows/release-pr.yml

@@ -12,7 +12,7 @@ permissions:
 
 concurrency:
   group: release-pr-${{ github.ref }}
-  cancel-in-progress: false
+  cancel-in-progress: true
 
 jobs:
   release-pr:
@@ -37,6 +37,16 @@ jobs:
       - name: Validate release metadata scripts
         run: bun run release:validate
 
+      - name: Close stale release PR
+        run: |
+          PR=$(gh pr list --head release-please--branches--main --json number --jq '.[0].number')
+          if [ -n "$PR" ]; then
+            echo "Closing stale release PR #$PR so release-please regenerates with full changelog"
+            gh pr close "$PR" --delete-branch=false
+          fi
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
       - name: Maintain release PR
         id: release
         uses: googleapis/release-please-action@v4.4.0