Approve fail-closed SCRAM validation after independent integration checks

Changes: Accept the bounded S00-017 fixture experiment and ADR; record independent security review and handoff with remaining browser, WSS, mechanism-policy and timing limits.
Validation: Fresh-cache npm ci and npm test passed on Node 24.21.0/npm 11.19.0 with 44 integrated tests. Verify exact installed pins, eight MIT notices, HTTPS/integrity and unchanged vendor files. make check passed 72 tooling tests; inspect executor scope/message and review metadata whitespace. No browser/server interoperability or constant-time assurance claimed.
