chore(sync): detect merge commits explicitly in post-commit hook

.githooks/post-commit

@@ -17,7 +17,16 @@ if [ ! -f "${CONF_FILE}" ] || [ ! -f "${SYNC_SCRIPT}" ]; then
 fi
 
 # Files changed in the commit we just made.
-changed="$(git diff-tree --no-commit-id --name-only -r HEAD 2>/dev/null || true)"
+# Merge commits: `git diff-tree HEAD` without a range returns the
+# combined-condensed diff (empty for clean, no-conflict merges),
+# which would skip regen on merges that bring in watched files via
+# the merged branch. Use a range against the first parent when HEAD
+# has two parents; plain HEAD for regular commits.
+if git rev-parse --verify HEAD^2 >/dev/null 2>&1; then
+  changed="$(git diff-tree --no-commit-id --name-only -r HEAD^1 HEAD 2>/dev/null || true)"
+else
+  changed="$(git diff-tree --no-commit-id --name-only -r HEAD 2>/dev/null || true)"
+fi
 if [ -z "${changed}" ]; then
   exit 0
 fi