feat: implement DoT/debuff runtime system (spec §6, AC-12, AC-13)

- Add ActiveEffect, EffectType types to game.ts; activeEffects + effectiveArmor on EnemyState
- Add SpellOnHitEffect + onHitEffect field to SpellDefinition
- Wire onHitEffect to fire (burn), death (curse), lightning (armor_corrode), frost (freeze), soul (bypassArmor burn)
- Add applyOnHitEffect() — applies on-hit effect on successful spell hit (spec §6.2)
- Add processDoTPhase() — ticks all active effects after weapon/golem attacks (spec §6.3)
- Add bypassArmor/bypassBarrier support in applyEnemyDefenses() (AC-13)
- Export standalone applyEnemyDefenses from combat-tick.ts for DoT pipeline
- Split DoT runtime into separate dot-runtime.ts (135 lines) to keep combat-actions.ts under 400 lines
- Update all enemy generation sites with activeEffects/effectiveArmor defaults
- Fix test helpers for new required fields

All 921 tests pass (45 test files)

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 } from '../types';
+import type { GameAction, SpellState, FloorState, GolemancyState, ActivityLogEntry, AchievementState, EquipmentSpellState, ActivityEventType, ActiveGolem, EnemyState } from '../types';
 import { getFloorMaxHP } from '../utils';
 import { generateFloorState } from '../utils/room-utils';
 import { addActivityLogEntry } from '../utils/activity-log';
@@ -302,6 +302,14 @@ export const useCombatStore = create<CombatStore>()(
         signedPacts: number[],
         golemancyState: { activeGolems: ActiveGolem[] },
         golemApplyDamageToRoom: (dmg: number) => { floorHP: number; floorMaxHP: number; roomCleared: boolean },
+        applyEnemyDefenses: (
+          dmg: number,
+          enemy: EnemyState | null,
+          roomType: string,
+          addLog: (msg: string) => void,
+          bypassArmor?: boolean,
+          bypassBarrier?: boolean,
+        ) => number,
       ) => {
         return processCombatTick(
           get,
@@ -315,6 +323,7 @@ export const useCombatStore = create<CombatStore>()(
           signedPacts,
           golemancyState,
           golemApplyDamageToRoom,
+          applyEnemyDefenses,
         );
       },