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/pipelines/combat-tick.ts

@@ -37,13 +37,62 @@ interface BuildCombatCallbacksParams {
   effects: ComputedEffects;
   maxMana: number;
   addLog: (msg: string) => void;
-  useCombatStore: { setState: (s: Record<string, unknown>) => void };
+  useCombatStore: { setState: (s: Record<string, unknown>) => void; getState: () => Record<string, unknown> };
   usePrestigeStore: { getState: () => { addDefeatedGuardian: (floor: number) => void } };
 }
 
 /** Speed-room bonus added to agile dodge chance (spec §4.5) */
 const SPEED_ROOM_DODGE_BONUS = 0.20;
 
+// ─── Standalone Enemy Defenses (for DoT/debuff pipeline) ─────────────────────
+
+/**
+ * Apply regular enemy defenses: dodge → barrier → armor (spec §5.2).
+ * Returns modified damage, or 0 on dodge.
+ * Exported for use by the DoT/debuff tick processing system (spec §6.3).
+ *
+ * @param bypassArmor — if true, skip armor reduction entirely (spec §6.4, AC-13)
+ * @param bypassBarrier — if true, skip barrier absorption (spec §6.4)
+ */
+export function applyEnemyDefenses(
+  dmg: number,
+  enemy: EnemyState | null,
+  roomType: string,
+  addLog: (msg: string) => void,
+  bypassArmor?: boolean,
+  bypassBarrier?: boolean,
+): number {
+  if (!enemy) return dmg;
+
+  // 1. Dodge check (spec §5.2, §4.5)
+  let effectiveDodge = enemy.dodgeChance;
+  if (roomType === 'speed') {
+    const hasAgile = enemy.name.toLowerCase().includes('agile');
+    if (hasAgile) {
+      effectiveDodge = Math.min(0.75, enemy.dodgeChance + SPEED_ROOM_DODGE_BONUS);
+    }
+  }
+  if (effectiveDodge > 0 && Math.random() < effectiveDodge) {
+    addLog('Attack dodged!');
+    return 0;
+  }
+
+  // 2. Barrier absorption (percentage, spec §5.2) — skipped if bypassBarrier
+  if (!bypassBarrier && enemy.barrier && enemy.barrier > 0) {
+    dmg *= (1 - enemy.barrier);
+  }
+
+  // 3. Armor reduction — skipped if bypassArmor (spec §6.4, AC-13)
+  if (!bypassArmor) {
+    const armorValue = (enemy as EnemyState & { effectiveArmor?: number }).effectiveArmor ?? enemy.armor;
+    if (armorValue && armorValue > 0) {
+      dmg *= (1 - armorValue);
+    }
+  }
+
+  return dmg;
+}
+
 export function buildCombatCallbacks(params: BuildCombatCallbacksParams) {
   const { ctx, effects, maxMana, useCombatStore, usePrestigeStore } = params;
 
@@ -85,46 +134,8 @@ export function buildCombatCallbacks(params: BuildCombatCallbacksParams) {
     return { ...enemy, barrier: recharged };
   };
 
-  /**
-   * Apply regular enemy defenses: dodge → barrier → armor (spec §5.2).
-   * Returns modified damage, or 0 on dodge.
-   * This is the single defense pipeline used for ALL enemy hits (not just guardians).
-   */
-  const applyEnemyDefenses = (
-    dmg: number,
-    enemy: EnemyState | null,
-    roomType: string,
-    addLog: (msg: string) => void,
-  ): number => {
-    if (!enemy) return dmg;
-
-    // 1. Dodge check (spec §5.2, §4.5)
-    let effectiveDodge = enemy.dodgeChance;
-    if (roomType === 'speed') {
-      // Agile + speed room: additive dodge bonus, capped at 0.75
-      const hasAgile = enemy.name.toLowerCase().includes('agile');
-      if (hasAgile) {
-        effectiveDodge = Math.min(0.75, enemy.dodgeChance + SPEED_ROOM_DODGE_BONUS);
-      }
-    }
-    if (effectiveDodge > 0 && Math.random() < effectiveDodge) {
-      addLog('Attack dodged!');
-      return 0;
-    }
-
-    // 2. Barrier absorption (percentage, spec §5.2)
-    if (enemy.barrier && enemy.barrier > 0) {
-      dmg *= (1 - enemy.barrier);
-    }
-
-    // 3. Armor reduction — use effectiveArmor (after corrode) if available, else base armor (spec §5.2)
-    const armorValue = (enemy as EnemyState & { effectiveArmor?: number }).effectiveArmor ?? enemy.armor;
-    if (armorValue && armorValue > 0) {
-      dmg *= (1 - armorValue);
-    }
-
-    return dmg;
-  };
+  // Local reference to the module-level applyEnemyDefenses
+  const defApply = applyEnemyDefenses;
 
   /**
    * Create the onDamageDealt callback for this tick.
@@ -150,7 +161,7 @@ export function buildCombatCallbacks(params: BuildCombatCallbacksParams) {
       }
 
       // Apply regular enemy defenses for ALL enemies (spec §5.2)
-      dmg = applyEnemyDefenses(dmg, defCtx.enemy, defCtx.roomType, addLog);
+      dmg = defApply(dmg, defCtx.enemy, defCtx.roomType, addLog);
 
       // Guardian-specific defensive pipeline (shield → barrier → health regen, spec §5.3)
       const guardian = getGuardianForFloor(ctx.combat.currentFloor);