stop-hook-forces-pristine-sweep-before-exit

The Stop hook (verification prompt) correctly blocked session exit when MEMORY.md had been edited 4 times without a full Pristine Sweep or Universal Completion Gate invocation. A VERIFY summary table listing what changed is insufficient — the hook requires evidence of HOW consistency was verified across the system. This caught 3 additional issues (infra count, excalidraw path, 3 missing architecture.md entries) that would have persisted.