Add snapshot, signature, and drift guard support for Vertex AI, Cloudflare Workers AI, and Perplexity API, backed by a queryable audit table and recent-window view.
This commit also wires the audit query layer into daily signal materialization and report generation so structure drift becomes a first-class signal instead of a log-only artifact.
Tighten real-ingestion success rules, separate scheduled reports from historical rebuilds, and persist source-level runtime audit across daily pipeline runs.
Also add the Phase 5 CI workflow contract plus verification updates and supporting docs so the full uncommitted change set can be validated together.
