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

docs/project-structure.txt

@@ -208,6 +208,7 @@ Mana-Loop/
 │       │   │   ├── mana-utils.test.ts
 │       │   │   ├── pact-utils.test.ts
 │       │   │   ├── regression-fixes.test.ts
+│       │   │   ├── room-utils-floor-state.test.ts
 │       │   │   ├── room-utils.test.ts
 │       │   │   ├── spire-utils.test.ts
 │       │   │   ├── store-actions-combat-prestige.test.ts
@@ -229,7 +230,6 @@ Mana-Loop/
 │       │   │   │   └── utility-spells.ts
 │       │   │   ├── core.ts
 │       │   │   ├── elements.ts
-│       │   │   ├── guardians.ts
 │       │   │   ├── index.ts
 │       │   │   ├── prestige.ts
 │       │   │   ├── rooms.ts
@@ -296,6 +296,7 @@ Mana-Loop/
 │       │   │   ├── enchantment-effects.ts
 │       │   │   ├── enchantment-types.ts
 │       │   │   ├── fabricator-recipes.ts
+│       │   │   ├── guardian-data.ts
 │       │   │   ├── guardian-encounters.ts
 │       │   │   └── loot-drops.ts
 │       │   ├── effects/