refactor: remove GUARDIANS constant, consolidate into guardian-data.ts

- Delete src/lib/game/constants/guardians.ts (the old static GUARDIANS constant)
- Create src/lib/game/data/guardian-data.ts with BASE_GUARDIANS (same data, new home)
- Remove GUARDIANS export from constants/index.ts
- Update all 11 files that imported GUARDIANS to use getGuardianForFloor() or BASE_GUARDIANS:
  - useGameDerived.ts, combat-actions.ts, gameStore.ts, prestigeStore.ts
  - combat-utils.ts, room-utils.ts, floor-utils.ts, spire-utils.ts
  - SpireCombatPage.tsx, SpireHeader.tsx
- Update 4 test files to use getGuardianForFloor() instead of GUARDIANS constant
- guardian-encounters.ts now imports BASE_GUARDIANS from guardian-data.ts
- Split room-utils.test.ts (505 lines) into room-utils.test.ts + room-utils-floor-state.test.ts

src/lib/game/utils/spire-utils.ts

@@ -2,10 +2,10 @@
 // Spire-specific utility functions for room generation, enemy stat scaling, etc.
 
 import type { RoomType, FloorState, EnemyState } from '../types';
-import { GUARDIANS, FLOOR_ELEM_CYCLE, PUZZLE_ROOMS } from '../constants';
+import { FLOOR_ELEM_CYCLE, PUZZLE_ROOMS } from '../constants';
 import { getFloorMaxHP, getFloorElement } from './floor-utils';
 import { getEnemyName } from './enemy-utils';
-import { isGuardianFloor, getExtendedGuardian } from '../data/guardian-encounters';
+import { getGuardianForFloor, isGuardianFloor } from '../data/guardian-encounters';
 
 // ─── Spire Room Configuration ─────────────────────────────────────────────────
 
@@ -85,7 +85,7 @@ export function generateSpireFloorState(floor: number, roomIndex: number, totalR
 
   switch (roomType) {
     case 'guardian': {
-      const guardian = GUARDIANS[floor] || getExtendedGuardian(floor);
+      const guardian = getGuardianForFloor(floor);
       if (guardian) {
         return {
           roomType: 'guardian',