Refactor large files into modular components

- Refactored page.tsx (613→252 lines) with GameOverScreen and LeftPanel extracted
- Refactored StatsTab.tsx (584→92 lines) with section components
- Refactored SkillsTab.tsx (434→54 lines) with sub-components
- Created modular structure for GameContext, LootInventory, and other components
- All extracted components organized into feature directories

src/lib/game/store-tests/element-recipes.test.ts

@@ -0,0 +1,32 @@
+/**
+ * Tests for Element Crafting Recipes
+ */
+
+import { describe, it, expect } from 'vitest';
+import { ELEMENTS } from '../constants';
+
+describe('Element Crafting Recipes', () => {
+  it('should have valid ingredient references', () => {
+    Object.entries(ELEMENTS).forEach(([id, def]) => {
+      if (def.recipe) {
+        def.recipe.forEach(ingredient => {
+          expect(ELEMENTS[ingredient]).toBeDefined();
+        });
+      }
+    });
+  });
+
+  it('should not have circular recipes', () => {
+    const visited = new Set<string>();
+    const checkCircular = (id: string, path: string[]): boolean => {
+      if (path.includes(id)) return true;
+      const def = ELEMENTS[id];
+      if (!def.recipe) return false;
+      return def.recipe.some(ing => checkCircular(ing, [...path, id]));
+    };
+    
+    Object.keys(ELEMENTS).forEach(id => {
+      expect(checkCircular(id, [])).toBe(false);
+    });
+  });
+});