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.

tools/lint/implementor-guidelines.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Stub lint: enforce docs tag placeholder until full checks land.
+if git diff --cached --name-only | grep -q '^docs/'; then
+  echo "[stub] docs touched: ensure commit includes 'docs:' trailer (value or 'n/a')"
+fi