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/gameStore.ts

@@ -1,7 +1,7 @@
 // Game Store — coordinator, tick pipeline, time/incursion
 import { create } from 'zustand';
 import { persist } from 'zustand/middleware';
-import { HOURS_PER_TICK, MAX_DAY } from '../constants';
+import { HOURS_PER_TICK, MAX_DAY, EQUIPMENT_TYPES } from '../constants';
 import { computeEquipmentEffects } from '../effects';
 import type { ComputedEffects } from '../effects/upgrade-effects.types';
 
@@ -303,6 +303,19 @@ export const useGameStore = create<GameCoordinatorStore>()(
             const activeEnemy = combatCbs.applyMageBarrierRecharge(primaryEnemy) ?? primaryEnemy;
             const defCtx = { roomType: ctx.combat.currentRoom?.roomType ?? 'combat', enemy: activeEnemy };
             const golemPipeline = buildGolemCombatPipeline(addLog);
+
+            // Build equipped swords map for melee auto-attack (spec §3.1)
+            const equippedSwords: Record<string, import('../types').EquipmentInstance> = {};
+            for (const [slot, instanceId] of Object.entries(ctx.crafting.equippedInstances || {})) {
+              if (!instanceId) continue;
+              const inst = ctx.crafting.equipmentInstances?.[instanceId];
+              if (!inst) continue;
+              const eqType = EQUIPMENT_TYPES[inst.typeId];
+              if (eqType?.category === 'sword') {
+                equippedSwords[instanceId] = inst;
+              }
+            }
+
             const combatResult = useCombatStore.getState().processCombatTick(
               rawMana, elements, maxMana, 1,
               combatCbs.onFloorCleared,
@@ -313,12 +326,13 @@ export const useGameStore = create<GameCoordinatorStore>()(
               (dmg, enemy, roomType, addLogFn, bypassArmor, bypassBarrier) => applyEnemyDefensesFromPipeline(
                 dmg, enemy, roomType, addLogFn, bypassArmor, bypassBarrier,
               ),
+              equippedSwords,
             );
             rawMana = combatResult.rawMana;
             elements = combatResult.elements;
             totalManaGathered += combatResult.totalManaGathered || 0;
             if (combatResult.logMessages) combatResult.logMessages.forEach(msg => addLog(msg));
-            writes.combat = { ...(writes.combat || {}), currentFloor: combatResult.currentFloor, floorHP: combatResult.floorHP, floorMaxHP: combatResult.floorMaxHP, maxFloorReached: combatResult.maxFloorReached, castProgress: combatResult.castProgress, equipmentSpellStates: combatResult.equipmentSpellStates, golemancy: { ...(writes.combat?.golemancy || ctx.combat.golemancy), activeGolems: combatResult.activeGolems } };
+            writes.combat = { ...(writes.combat || {}), currentFloor: combatResult.currentFloor, floorHP: combatResult.floorHP, floorMaxHP: combatResult.floorMaxHP, maxFloorReached: combatResult.maxFloorReached, castProgress: combatResult.castProgress, equipmentSpellStates: combatResult.equipmentSpellStates, golemancy: { ...(writes.combat?.golemancy || ctx.combat.golemancy), activeGolems: combatResult.activeGolems }, meleeSwordProgress: combatResult.meleeSwordProgress };
           }
 
           if (ctx.combat.currentAction === 'craft') {