fix(ai): migrate drift check and evidence gate to QPK v2 task service

[Pigbibi]

Follows CryptoStrategies #265.

• Drift Check: pin QPK reusable workflow and checkout to eae362bd3e3fad5be59a7615eeba10be839a9934; drop retired ai_gateway_service_url / codex_audit_service_url wiring; pass ai_service_url, ai_service_audience, ai_service_reviewers_json from repo variables. The provider (Dot) is selected by the service-side project policy.
• Evidence Gate: remove the AIAuditBridge checkout and retired Codex/Gateway env. The old path silently passed because run_dual_review_pipeline.py no longer exists in AIAuditBridge; the gate now uses QPK task_review.review_material with three roles and fails closed (exit 3 when unavailable/pending, exit 1 unless unanimous advisory approval).
• Synthetic tests only. No secrets, no deployment, no change to the HK annualization/data issue.