E23 Continuous Assurance MVP + MCPGate enforcement

Clean-room result: VALID (?/13 checks). Invariants 20 all-hold=True; attacks 12 all-contained=True; tests passed=30.

Verify: python3 verify_e23.py . · REPRODUCE.txt · manifest.json

Honest: same-project clean room, NOT third-party verification; no production claim.