gateFailureFingerprints held one slot per gate, so the budget only charged
when a failure repeated back to back. Whack-a-mole (fix A breaks B, fix B
breaks A) alternates two fingerprints forever, every round read as progress,
and the per-gate budget never triggered. Track the full set seen per gate and
charge when the current fingerprint is a repeat.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>