fix(ci): track-bst-sources: use --squash for auto-merge, not --merge

The repo has allowMergeCommit=false — only squash merges are permitted.
The previous --merge call silently fell through to the warning echo,
leaving auto-merge never set on tracking PRs. Switch to --squash.

Assisted-by: Claude Sonnet 4.6 via pi

Author: castrojo

.github/workflows/track-bst-sources.yml

@@ -263,9 +263,9 @@ jobs:
 
           if [ "${{ matrix.group }}" = "auto-merge" ]; then
             echo "Enabling auto-merge..."
-            # Use --merge to match the merge queue's required merge_method=MERGE.
-            # --squash conflicts with the merge queue ruleset and prevents auto-queuing.
-            gh pr merge "$PR_URL" --auto --merge || echo "::warning::Could not enable auto-merge"
+            # Use --squash: the repo only allows squash merges (allowMergeCommit=false).
+            # --merge would silently fail via the '|| echo ::warning::' fallback.
+            gh pr merge "$PR_URL" --auto --squash || echo "::warning::Could not enable auto-merge"
           fi
 
   track-tarballs: