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/pack.json

@@ -0,0 +1,18 @@
+{
+  "pack_id": "at-guardrails",
+  "version": "0.1.0-stub",
+  "inputs_lock": "tests/acceptance/packs/guardrails/inputs.lock",
+  "signers": ["stub-key-id"],
+  "fixtures": [
+    {"id": "AT1-admission", "expected": "expected/at1.json", "artifact": "fixtures/at1"},
+    {"id": "AT2-vex", "expected": "expected/at2.json", "artifact": "fixtures/at2"},
+    {"id": "AT3-authz", "expected": "expected/at3.json", "artifact": "fixtures/at3"},
+    {"id": "AT4-replay-parity", "expected": "expected/at4.json", "artifact": "fixtures/at4"},
+    {"id": "AT5-policy-dsse-negative", "expected": "expected/at5.json", "artifact": "fixtures/at5"},
+    {"id": "AT6-pitr-rehearsal", "expected": "expected/at6.json", "artifact": "fixtures/at6"},
+    {"id": "AT7-offline-guardrail-pack", "expected": "expected/at7.json", "artifact": "fixtures/at7"},
+    {"id": "AT8-gating-thresholds", "expected": "expected/at8.json", "artifact": "fixtures/at8"},
+    {"id": "AT9-reporting-slo", "expected": "expected/at9.json", "artifact": "fixtures/at9"},
+    {"id": "AT10-schema-signing", "expected": "expected/at10.json", "artifact": "fixtures/at10"}
+  ]
+}