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.)

src/lib/game/stores/gameHooks.ts

@@ -1,13 +1,12 @@
+import { useEffect } from 'react';
 import { useGameStore } from './gameStore';
 import { TICK_MS } from '../constants';
 
 export function useGameLoop() {
   const tick = useGameStore((s) => s.tick);
 
-  return {
-    start: () => {
-      const interval = setInterval(tick, TICK_MS);
-      return () => clearInterval(interval);
-    },
-  };
+  useEffect(() => {
+    const interval = setInterval(tick, TICK_MS);
+    return () => clearInterval(interval);
+  }, [tick]);
 }