chore: import upstream snapshot with attribution

tests/server/test_source_batch_parity.py

@@ -0,0 +1,33 @@
+"""Anti-drift gate: the neutral ``_app.source_batch`` fatal set matches REST's status table.
+
+``_app.source_batch`` cannot import the FastAPI-tainted ``CATEGORY_STATUS`` (the
+``_app`` import boundary forbids ``server``/``fastapi``), so it expresses "fatal" as
+an explicit ``frozenset[ErrorCategory]``. This gate — which CAN import both, since it
+lives under ``tests/server`` — proves that frozenset equals the categories whose
+``CATEGORY_STATUS`` projection is 401 / 429 / >=500. If a future taxonomy change
+diverges the two, this fails loudly.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+# CATEGORY_STATUS lives in the fastapi-importing server module.
+pytest.importorskip("fastapi")
+
+from notebooklm._app.errors import ErrorCategory  # noqa: E402 - after importorskip guard
+from notebooklm._app.source_batch import _FATAL_CATEGORIES  # noqa: E402 - after importorskip guard
+from notebooklm.server._errors import CATEGORY_STATUS  # noqa: E402 - after importorskip guard
+
+
+def test_fatal_categories_match_rest_status_partition() -> None:
+    expected = {
+        category
+        for category, status in CATEGORY_STATUS.items()
+        if status in (401, 429) or status >= 500
+    }
+    assert expected == _FATAL_CATEGORIES
+
+
+def test_fatal_categories_are_all_real_categories() -> None:
+    assert set(ErrorCategory) >= _FATAL_CATEGORIES