[codex] Record Base canary source verification

[FlowmemoryAI]

Summary

Records the completed BaseScan source verification pass for the Base canary deployment and hardens the verification helper after the live submit run:

• documents that all 10 current Base canary addresses are source-verified;
• adds a non-secret verification status artifact with BaseScan URLs and source commits;
• clarifies that FlowMemoryHookAdapter was verified against deployment-source commit 11d562c, while current main contains the newer v4-shaped callback source;
• redacts the BaseScan API key from verification helper error paths;
• adds --continue-on-error and --delay-ms support for explorer rate-limit handling.

Validation

• node --check infra/scripts/verify-base-canary-sources.mjs
• npm run verify:base-canary:sources -- --check-bytecode --rpc-url https://mainnet.base.org --json
• npm run launch:candidate

Security note

The API key used for verification was not committed. Because it appeared in chat and one pre-fix error path, it should be rotated outside the repo.