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/hooks/useGameDerived.ts

@@ -18,7 +18,8 @@ import {
   getElementalBonus,
 } from '../utils';
 import { computePactMultiplier, computePactInsightMultiplier } from '../utils/pact-utils';
-import { ELEMENTS, GUARDIANS, SPELLS_DEF, getStudySpeedMultiplier, getStudyCostMultiplier, HOURS_PER_TICK, TICK_MS } from '../constants';
+import { ELEMENTS, SPELLS_DEF, getStudySpeedMultiplier, getStudyCostMultiplier, HOURS_PER_TICK, TICK_MS } from '../constants';
+import { getGuardianForFloor } from '../data/guardian-encounters';
 import { hasSpecial, SPECIAL_EFFECTS } from '../effects/special-effects';
 
 /**
@@ -123,12 +124,12 @@ export function useCombatStats() {
   );
 
   const isGuardianFloor = useMemo(
-    () => !!GUARDIANS[currentFloor],
+    () => !!getGuardianForFloor(currentFloor),
     [currentFloor]
   );
 
   const currentGuardian = useMemo(
-    () => GUARDIANS[currentFloor],
+    () => getGuardianForFloor(currentFloor),
     [currentFloor]
   );