tests/cmd(fix[GitRemote]): handle unchanged HEAD in set_head test

why: CI failed because git returns "unchanged" when HEAD is already set,
but assertion only checked for "set to".
what:
- Add "unchanged" as valid response in set_head auto assertion

Author: tony

tests/cmd/test_git.py

@@ -581,7 +581,8 @@ def test_remote_set_head(
 
     # set_head returns either confirmation message or empty string
     if auto:
-        assert "set to" in result.lower() or result == ""
+        result_lower = result.lower()
+        assert "set to" in result_lower or "unchanged" in result_lower or result == ""
     else:
         assert result == "" or "head" in result.lower()