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/crafting-actions/computed-getters.ts

@@ -0,0 +1,56 @@
+// ─── Computed Getters ──────────────────────────────────────────────────────
+
+import type { GameState } from '../types';
+import { ENCHANTMENT_EFFECTS } from '../data/enchantment-effects';
+
+export function getEquipmentSpells(get: () => GameState): string[] {
+  const state = get();
+  const spells: string[] = [];
+
+  for (const instanceId of Object.values(state.equippedInstances)) {
+    if (!instanceId) continue;
+    const instance = state.equipmentInstances[instanceId];
+    if (!instance) continue;
+
+    for (const ench of instance.enchantments) {
+      const effectDef = ENCHANTMENT_EFFECTS[ench.effectId];
+      if (effectDef?.effect.type === 'spell' && effectDef.effect.spellId) {
+        spells.push(effectDef.effect.spellId);
+      }
+    }
+  }
+
+  return [...new Set(spells)];
+}
+
+export function getEquipmentEffects(get: () => GameState): Record<string, number> {
+  const state = get();
+  const effects: Record<string, number> = {};
+
+  for (const instanceId of Object.values(state.equippedInstances)) {
+    if (!instanceId) continue;
+    const instance = state.equipmentInstances[instanceId];
+    if (!instance) continue;
+
+    for (const ench of instance.enchantments) {
+      const effectDef = ENCHANTMENT_EFFECTS[ench.effectId];
+      if (!effectDef) continue;
+
+      if (effectDef.effect.type === 'bonus' && effectDef.effect.stat && effectDef.effect.value) {
+        effects[effectDef.effect.stat] = (effects[effectDef.effect.stat] || 0) + effectDef.effect.value * ench.stacks;
+      }
+    }
+  }
+
+  return effects;
+}
+
+export function getAvailableCapacity(
+  instanceId: string,
+  get: () => GameState
+): number {
+  const state = get();
+  const instance = state.equipmentInstances[instanceId];
+  if (!instance) return 0;
+  return instance.totalCapacity - instance.usedCapacity;
+}