feat: Implement Policy Engine Evaluation Service and Cache with unit tests

Temp commit to debug

docs/modules/policy/architecture.md

@@ -179,9 +179,10 @@ Determinism guard instrumentation wraps the evaluator, rejecting access to forbi
 - **Queue:** Mongo queue with lease; each job assigned `leaseDuration`, `maxAttempts`.
 - **Workers:** Lease jobs, execute evaluation pipeline, report status (success/failure/canceled). Failures with recoverable errors requeue with backoff; determinism or schema violations mark job `failed` and raise incident event.
 - **Fairness:** Round-robin per `{tenant, policyId}`; emergency jobs (`priority=emergency`) jump queue but limited via circuit breaker.
-- **Replay:** On demand, orchestrator rehydrates run via stored cursors and exports sealed bundle for audit/CI determinism checks.
-
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+- **Replay:** On demand, orchestrator rehydrates run via stored cursors and exports sealed bundle for audit/CI determinism checks.
+- **Batch evaluation service (`/api/policy/eval/batch`):** Stateless evaluator powering Findings Ledger and replay/offline workflows. Requests contain canonical ledger events plus optional current projection; responses return status/severity/labels/rationale without mutating state. Policy Engine enforces per-tenant cost budgets, caches results by `(tenantId, policyVersion, eventHash, projectionHash)`, and falls back to inline evaluation when the remote service is disabled.
+
+---
 
 ## 7 · Security & Tenancy