Summary

Turns two crash-on-unsupported patterns into assertion failures: the $out tests index
into listCollections after a failed $out, and the planCacheSetFilter tests subscript
indexFilterSet. I checked the $out change with a stubbed executor that makes $out
fail: main raises IndexError, this branch raises an AssertionError carrying the
engine's error. CI is green on both mongo targets. One file with the same $out pattern
is not covered (item 1).

Critical Issues

1. [Required] test_out_write_behavior.py:100 has the same crash and is not changed.
   test_out_database_name_acceptance calls $out, discards the result, then reads
   cast(dict, result)["cursor"]["firstBatch"][0] from listCollections. An engine that
   rejects $out still gets an IndexError there. It is the third file with this pattern
   (grep 'firstBatch"\]\[0\]' in stages/out/ finds exactly these three). Please apply
   the same fix, or say why this file is excluded.

Positive Feedback

• The root cause is correctly identified: the crash hides the engine's actual error.
• The scope is small, and the description says what was run (57 and 24 passed on MongoDB 8.2.4).
• .get() for indexFilterSet is correct for the assertion. A missing field yields None,
  which Eq(True) rejects, so no test can switch from failing to passing.