feat: add PolicyPackSelectorComponent with tests and integration

- Implemented PolicyPackSelectorComponent for selecting policy packs.
- Added unit tests for component behavior, including API success and error handling.
- Introduced monaco-workers type declarations for editor workers.
- Created acceptance tests for guardrails with stubs for AT1–AT10.
- Established SCA Failure Catalogue Fixtures for regression testing.
- Developed plugin determinism harness with stubs for PL1–PL10.
- Added scripts for evidence upload and verification processes.

tests/acceptance/packs/guardrails/inputs.lock

@@ -0,0 +1,9 @@
+scanner_version: "stella-scanner 0.9.0-offline"
+db_version: "mongo 6.0.12"
+policy_engine_version: "stella-policy 0.8.4"
+seeds:
+  default: 1337
+  replay: 4242
+feeds_snapshot: "offline-cache-2025-11-30"
+tz: "UTC"
+notes: "Deterministic replay; no network calls"