[realcodesiman]

Summary

• Allow realtime streams and revoke markers to use a dedicated Redis deployment while preserving the existing REDIS_URL fallback.
• Keep Builder, Worker, and the realtime gateway on one explicitly documented endpoint.

Changes

• Validate and prefer REDIS_REALTIME_URL in realtime gateway and publisher configuration.
• Add gateway and business resolver coverage for override and fallback behavior.
• Document the cutover configuration and retention implications.

Test plan

• pnpm ultracite fix (pre-commit hook)
• Workspace check-types (pre-commit hook; includes realtime and business)
• Manual deployment verification