fix: improve auto-merge in update-version workflow

Changes:
- Use GH_PAT (if available) for better permissions
- Extract PR number for more reliable merge command
- Add detailed error logging with exit codes
- Attempt auto-merge on existing PRs
- Provide clear troubleshooting guidance

This should help diagnose why auto-merge is failing and potentially
fix permission issues if a GH_PAT secret is configured.

https://claude.ai/code/session_015R3U3kiprQiNTTNNt31Sg6

.github/workflows/update-version.yml

@@ -112,7 +112,7 @@ jobs:
       - name: Create Pull Request
         if: steps.check_changes.outputs.has_changes == 'true' || steps.check_changes.outputs.force_mode == 'true'
         env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_TOKEN: ${{ secrets.GH_PAT || secrets.GITHUB_TOKEN }}
         run: |
           BRANCH_NAME="update-version/stable"
           FORCE="${{ inputs.force }}"
@@ -168,18 +168,34 @@ jobs:
           if [ $PR_CREATE_EXIT -eq 0 ]; then
             echo "✅ PR created successfully: $PR_URL"
 
+            # Extract PR number from URL
+            PR_NUMBER=$(echo "$PR_URL" | grep -oP '\d+$')
+            echo "📋 PR Number: #$PR_NUMBER"
+
             # Auto-merge the PR (squash merge)
             # Note: This requires branch protection rules to be satisfied
             # If checks haven't completed yet, auto-merge will queue the merge
             echo "Attempting to enable auto-merge..."
-            if gh pr merge "$BRANCH_NAME" --squash --auto --delete-branch 2>/dev/null; then
+            set +e
+            MERGE_OUTPUT=$(gh pr merge "$PR_NUMBER" --squash --auto --delete-branch 2>&1)
+            MERGE_EXIT=$?
+            set -e
+
+            if [ $MERGE_EXIT -eq 0 ]; then
               echo "✅ Auto-merge enabled - PR will merge automatically when checks pass"
+              echo "$MERGE_OUTPUT"
             else
-              echo "⚠️ Auto-merge not available - PR created for manual review"
-              echo "This may happen if:"
+              echo "⚠️ Auto-merge failed with exit code $MERGE_EXIT"
+              echo "Output: $MERGE_OUTPUT"
+              echo ""
+              echo "Possible reasons:"
               echo "  - Required status checks haven't completed yet"
               echo "  - Branch protection rules require manual approval"
-              echo "  - Insufficient permissions (see workflow permissions comment)"
+              echo "  - Insufficient permissions (try adding GH_PAT secret with repo scope)"
+              echo "  - Auto-merge feature not enabled in repository settings"
+              echo ""
+              echo "💡 Consider creating a Personal Access Token (PAT) with 'repo' scope"
+              echo "   and adding it as a repository secret named 'GH_PAT'"
             fi
           else
             # PR creation failed - could be duplicate or other error
@@ -191,6 +207,15 @@ jobs:
             if [ -n "$EXISTING_PR" ]; then
               echo "ℹ️ PR already exists for branch $BRANCH_NAME"
               echo "$EXISTING_PR"
+
+              # Try to enable auto-merge on existing PR
+              PR_NUMBER=$(echo "$EXISTING_PR" | grep -oP '^\d+')
+              if [ -n "$PR_NUMBER" ]; then
+                echo "Attempting to enable auto-merge on existing PR #$PR_NUMBER..."
+                set +e
+                gh pr merge "$PR_NUMBER" --squash --auto --delete-branch 2>&1
+                set -e
+              fi
             else
               echo "❌ PR creation failed with error:"
               echo "$PR_URL"