fix(golden): make update_goldens.py / check_semver_bump.py work as direct scripts

Both scripts have docstrings and corpus-test failure hints that tell users
to invoke them as `python tests/golden/<script>.py ...` from the repo root.
But Python does not auto-add the repo root to sys.path for direct script
invocation, so the absolute `from tests.golden...` imports fail with
ModuleNotFoundError.

Prepend the repo root to sys.path when each script is run as __main__,
gated on `__package__ is None` so the module form continues to work.

Author: bnusunny

tests/golden/check_semver_bump.py

@@ -7,6 +7,18 @@
 
 from __future__ import annotations
 
+# Allow direct script invocation (`python tests/golden/check_semver_bump.py`)
+# in addition to module form (`python -m tests.golden.check_semver_bump`).
+# When run as a script, Python does not auto-add the repo root to sys.path,
+# so absolute imports rooted at `tests.golden...` would fail. This script
+# happens to have no such imports today, but keep the guard symmetrical with
+# update_goldens.py so future imports do not silently regress the script form.
+if __name__ == "__main__" and __package__ is None:
+    import sys
+    from pathlib import Path
+
+    sys.path.insert(0, str(Path(__file__).resolve().parents[2]))
+
 import argparse
 import re
 import subprocess

tests/golden/update_goldens.py

@@ -10,6 +10,16 @@
 
 from __future__ import annotations
 
+# Allow direct script invocation (`python tests/golden/update_goldens.py`)
+# in addition to module form (`python -m tests.golden.update_goldens`).
+# When run as a script, Python does not auto-add the repo root to sys.path,
+# so the absolute `from tests.golden...` imports below would fail.
+if __name__ == "__main__" and __package__ is None:
+    import sys
+    from pathlib import Path
+
+    sys.path.insert(0, str(Path(__file__).resolve().parents[2]))
+
 import argparse
 import difflib
 import fnmatch