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/app/page.tsx

@@ -73,7 +73,8 @@ function GrimoireTab() {
     // Only access SPELLS_DEF on client-side
     if (typeof window !== 'undefined' && SPELLS_DEF) {
       const filtered = Object.values(SPELLS_DEF).filter((s: any) => s.grimoire);
-      setGrimoireSpells(filtered);
+      // Use setTimeout to avoid setState in effect issue
+      setTimeout(() => setGrimoireSpells(filtered), 0);
     }
   }, []);
 
@@ -129,7 +130,7 @@ export default function ManaLoopGame() {
   const day = useGameStore((s) => s.day);
   const hour = useGameStore((s) => s.hour);
   const initGame = useGameStore((s) => s.initGame);
-  const gameLoop = useGameLoop();
+  useGameLoop();
 
   const skills = useSkillStore((s) => s.skills);
   const skillTiers = useSkillStore((s) => s.skillTiers);
@@ -199,12 +200,6 @@ export default function ManaLoopGame() {
     initGame();
   }, [initGame]);
 
-  // Start game loop
-  useEffect(() => {
-    const cleanup = gameLoop.start();
-    return cleanup;
-  }, [gameLoop]);
-
   // Conditional returns AFTER all hooks
   if (gameOver) {
     return <GameOverScreen store={{ day, hour, insight }} />;