Update documentation for Sub-Task 3 completion

- Marked Sub-Task 3 as completed in todo.md
- Updated subtask_3_progress.md with completion status and notes

src/lib/game/store.ts

@@ -46,7 +46,7 @@ import {
   type CraftingActions 
 } from './crafting-slice';
 import { getActiveEquipmentSpells, type ActiveEquipmentSpell } from './utils/combat-utils';
-import { EQUIPMENT_TYPES } from './data/equipment';
+import { EQUIPMENT_TYPES, getValidSlotsForEquipmentType } from './data/equipment';
 import { ENCHANTMENT_EFFECTS, calculateEffectCapacityCost } from './data/enchantment-effects';
 import { ATTUNEMENTS_DEF, getTotalAttunementRegen, getAttunementConversionRate, getAttunementXPForLevel, MAX_ATTUNEMENT_LEVEL } from './data/attunements';
 import { GOLEMS_DEF, getGolemSlots, isGolemUnlocked, getGolemDamage, getGolemAttackSpeed, getGolemFloorDuration, canAffordGolemSummon, deductGolemSummonCost, canAffordGolemMaintenance, deductGolemMaintenance } from './data/golems';
@@ -2212,12 +2212,18 @@ export const useGameStore = create<GameStore>()(
         if (!type) return false;
 
         // Check if equipment can go in this slot
-        const validSlots = type.category === 'accessory'
-          ? ['accessory1', 'accessory2']
-          : [type.slot];
+        const validSlots = getValidSlotsForEquipmentType(type);
 
         if (!validSlots.includes(slot)) return false;
 
+        // BLOCK: Prevent equipping anything in offhand if a 2-handed weapon is in mainHand
+        if (slot === 'offHand' && state.equippedInstances.mainHand) {
+          const mainHandType = EQUIPMENT_TYPES[state.equippedInstances.mainHand];
+          if (mainHandType?.twoHanded) {
+            return false; // Cannot equip to offhand while 2H weapon is equipped
+          }
+        }
+
         // Check if slot is occupied
         const currentEquipped = state.equippedInstances[slot];
         if (currentEquipped === instanceId) return true; // Already equipped here
@@ -2233,6 +2239,11 @@ export const useGameStore = create<GameStore>()(
         // Equip to new slot
         newEquipped[slot] = instanceId;
 
+        // If equipping a 2-handed weapon to mainHand, clear offHand
+        if (slot === 'mainHand' && type.twoHanded && newEquipped.offHand) {
+          newEquipped.offHand = null;
+        }
+
         set(() => ({ equippedInstances: newEquipped }));
         return true;
       },