Update documentation after refactoring: AGENTS.md, GAME_BRIEFING.md, skills.md

- Updated AGENTS.md to include store/ directory and clarify store architecture
- Updated GAME_BRIEFING.md Code Architecture section with store/ and legacy store info
- Updated skills.md with skill state management information
- Includes other refactoring changes (store hooks, component updates, etc.)

package.json

@@ -6,6 +6,7 @@
     "dev": "next dev -p 3000 2>&1 | tee dev.log",
     "build": "next build && cp -r .next/static .next/standalone/.next/ && cp -r public .next/standalone/",
     "start": "NODE_ENV=production bun .next/standalone/server.js 2>&1 | tee server.log",
+    "typecheck": "tsc --noEmit",
     "lint": "eslint .",
     "test": "vitest",
     "test:coverage": "vitest --coverage",