feat: PrismFacet core implementation

- Plugin scaffold: manifest, tsconfig, package.json
- Router loader with dynamic import + cache busting for hot reload
- Rule store: CRUD on rules.json
- Prompt injector: resolve routers → match rules → read files → inject
- MCP tool: prompt_rules (add/remove/list/test/reload-routers/list-routers)
- Built-in routers: agent-id (zero-dep), role, position (ego.json)
- before_prompt_build hook for system prompt injection

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tsconfig.json

@@ -0,0 +1,16 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "outDir": "dist",
+    "rootDir": "src",
+    "declaration": true,
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true
+  },
+  "include": ["src/**/*"]
+}