fix: address Octocode review — move size check, add tests for all 3 fixes

- Move file size check before try block so IOError propagates cleanly
  (not caught by the except OSError handler below it)
- Wrap os.path.getsize in its own try/except to preserve existing
  test_normalize_io_error behavior on missing files
- Add test_normalize_rejects_large_file (mocked getsize)
- Add test_null_arguments_does_not_hang (#394)
- Add test_cmd_repair_trailing_slash_does_not_recurse (#395)

532 tests pass locally, 0 regressions.

tests/test_normalize.py

@@ -499,3 +499,13 @@ def test_messages_to_transcript_assistant_first():
     result = _messages_to_transcript(msgs, spellcheck=False)
     assert "preamble" in result
     assert "> Q" in result
+
+
+def test_normalize_rejects_large_file():
+    """Files over 500 MB should raise IOError before reading."""
+    with patch("mempalace.normalize.os.path.getsize", return_value=600 * 1024 * 1024):
+        try:
+            normalize("/fake/huge_file.txt")
+            assert False, "Should have raised IOError"
+        except IOError as e:
+            assert "too large" in str(e).lower()