feat: implement sword/melee auto-attack system (spec §3.1, §4.3)

- Add calcMeleeDamage() with elemental matchup for enchanted swords
- Add meleeSwordProgress per-instance accumulator to combat state
- Add melee branch in processCombatTick (no mana cost, no Executioner/Berserker)
- Add baseDamage/attackSpeed stats to all 5 sword types
- Wire equippedSwords through gameStore to combat tick pipeline
- 16 new regression tests, all 937 tests pass

src/lib/game/stores/combatStore.ts

@@ -4,7 +4,7 @@
 import { create } from 'zustand';
 import { persist } from 'zustand/middleware';
 import { createSafeStorage } from '../utils/safe-persist';
-import type { GameAction, SpellState, FloorState, GolemancyState, ActivityLogEntry, AchievementState, EquipmentSpellState, ActivityEventType, ActiveGolem, EnemyState } from '../types';
+import type { GameAction, SpellState, FloorState, GolemancyState, ActivityLogEntry, AchievementState, EquipmentSpellState, ActivityEventType, ActiveGolem, EnemyState, EquipmentInstance } from '../types';
 import { getFloorMaxHP } from '../utils';
 import { generateFloorState } from '../utils/room-utils';
 import { addActivityLogEntry } from '../utils/activity-log';
@@ -66,6 +66,9 @@ export const useCombatStore = create<CombatStore>()(
       comboHitCount: 0,
       floorHitCount: 0,
 
+      // Melee sword progress accumulators (spec §3.1)
+      meleeSwordProgress: {},
+
       // Guardian defensive state
       guardianShield: 0,
       guardianShieldMax: 0,
@@ -310,6 +313,7 @@ export const useCombatStore = create<CombatStore>()(
           bypassArmor?: boolean,
           bypassBarrier?: boolean,
         ) => number,
+        equippedSwords?: Record<string, EquipmentInstance>,
       ) => {
         return processCombatTick(
           get,
@@ -324,6 +328,7 @@ export const useCombatStore = create<CombatStore>()(
           golemancyState,
           golemApplyDamageToRoom,
           applyEnemyDefenses,
+          equippedSwords,
         );
       },
 
@@ -372,6 +377,7 @@ export const useCombatStore = create<CombatStore>()(
         guardianShieldMax: state.guardianShieldMax,
         guardianBarrier: state.guardianBarrier,
         guardianBarrierMax: state.guardianBarrierMax,
+        meleeSwordProgress: state.meleeSwordProgress,
       }),
     }
   )