fix: spire combat 11 high-severity discrepancies (issue #333)

D-01: Implement per-weapon cast progress (weaponCastProgress record)
D-04: Bypass Executioner/Berserker discipline specials for golem attacks
D-09: Fix lightning counter direction (lightning→water, not lightning→earth)
D-10: Add full composite element counters (blackflame/radiantflames ↔ frost/water/light/dark)
D-15: Fix Executioner to check per-enemy HP < 25% instead of floorHP ratio
D-20: Fix dodge formula to match spec (min(0.55, floor × 0.003), starts at 0)
D-22: Fix shield modifier to use flat HP pool instead of percentage barrier
D-23: Wire up applyMageBarrierRecharge in the damage pipeline
D-25: Move guardian regen from per-damage-event to once-per-tick
D-26: Add guardian armor reduction to the guardian defensive pipeline
D-31: Fix armor_corrode to be temporary (restore armor on effect expiry)
D-38: Implement AoE damage distribution across enemies

All 1069 tests pass. No files exceed 400 lines.

src/lib/game/stores/combat-damage.ts

@@ -23,11 +23,12 @@ export function lowestHPEnemy(enemies: EnemyState[]): EnemyState | null {
  * Apply damage to enemies in the current room.
  *
  * Spec §3.2:
- * - AoE spells: each enemy takes full damage
+ * - AoE spells: damage is distributed across up to aoeTargets enemies
  * - Single-target: target the enemy with lowest HP (focus-fire)
  * - Recalculates floorHP as sum of all enemy HP
  * - Triggers onRoomCleared when all enemies reach 0 HP
  *
+ * @param aoeTargets — max number of enemies hit by AoE (spec §3.2, D-38 fix)
  * @returns { floorHP, floorMaxHP, roomCleared }
  */
 export function applyDamageToRoom(
@@ -35,6 +36,7 @@ export function applyDamageToRoom(
   set: (state: Partial<CombatState>) => void,
   dmg: number,
   isAoe: boolean,
+  aoeTargets?: number,
 ): { floorHP: number; floorMaxHP: number; roomCleared: boolean } {
   const state = get();
   const room = state.currentRoom;
@@ -48,11 +50,23 @@ export function applyDamageToRoom(
   // For single-target, find the lowest HP enemy once (focus-fire)
   const singleTarget = isAoe ? null : lowestHPEnemy(room.enemies);
 
+  // For AoE, select up to aoeTargets living enemies (focus-fire: lowest HP first)
+  let aoeTargetSet: Set<string> | null = null;
+  if (isAoe && aoeTargets && aoeTargets > 0) {
+    const livingEnemies = room.enemies
+      .filter(e => e.hp > 0)
+      .sort((a, b) => a.hp - b.hp);
+    const targets = livingEnemies.slice(0, aoeTargets);
+    aoeTargetSet = new Set(targets.map(e => e.id));
+  }
+
   const updatedEnemies = room.enemies.map((enemy) => {
     if (enemy.hp <= 0) return enemy;
     if (isAoe) {
-      // AoE: each enemy takes full damage
-      return { ...enemy, hp: Math.max(0, enemy.hp - dmg) };
+      // AoE: distribute damage across up to aoeTargets enemies (spec §3.2, D-38 fix)
+      if (aoeTargetSet && !aoeTargetSet.has(enemy.id)) return enemy;
+      const dmgPerEnemy = aoeTargetSet ? dmg / aoeTargetSet.size : dmg;
+      return { ...enemy, hp: Math.max(0, enemy.hp - dmgPerEnemy) };
     }
     // Single-target: only damage the lowest HP enemy
     if (singleTarget && enemy.id === singleTarget.id) {