feat: implement Room Enchantments system for Enchanter attunement

- Add roomEnchantment field to FloorState (coverage meter 0-100)
- Add 8 room enchantment effect definitions (fire/frost/death/lightning/dark/earth/transference)
- Add room-enchanting discipline with perks (room-coverage-rate capped, resonant-stamps once, 8 unlock perks)
- Add room enchantment combat tick phase (after DoT) with coverage growth and effect application
- Add coverage carryover between rooms via resonant-stamps perk
- Add RoomDisplay coverage bar and effect magnitude UI
- Add room-enchantments-utils.ts for coverage/effect computation
- Extract combat-room-enchantments.ts to keep combat-actions.ts under 400 lines
- Add 25 tests covering all acceptance criteria (AC-1 through AC-22)

docs/project-structure.txt

@@ -249,6 +249,7 @@ Mana-Loop/
 │   │   │   │   ├── persistence.test.ts
 │   │   │   │   ├── regression-fixes.test.ts
 │   │   │   │   ├── reset-game-comprehensive.test.ts
+│   │   │   │   ├── room-enchantments.test.ts
 │   │   │   │   ├── room-utils-floor-state.test.ts
 │   │   │   │   ├── room-utils.test.ts
 │   │   │   │   ├── spell-cast-floorhp-guard.test.ts
@@ -301,6 +302,7 @@ Mana-Loop/
 │   │   │   │   │   ├── elemental-regen-advanced.ts
 │   │   │   │   │   ├── elemental-regen.ts
 │   │   │   │   │   ├── elemental.ts
+│   │   │   │   │   ├── enchanter-combat.ts
 │   │   │   │   │   ├── enchanter-special.ts
 │   │   │   │   │   ├── enchanter-spells.ts
 │   │   │   │   │   ├── enchanter-utility.ts
@@ -394,6 +396,7 @@ Mana-Loop/
 │   │   │   │   ├── combat-invocation.ts
 │   │   │   │   ├── combat-melee.ts
 │   │   │   │   ├── combat-reset.ts
+│   │   │   │   ├── combat-room-enchantments.ts
 │   │   │   │   ├── combat-state.types.ts
 │   │   │   │   ├── combatStore.ts
 │   │   │   │   ├── crafting-equipment-tick.ts
@@ -448,6 +451,7 @@ Mana-Loop/
 │   │   │   │   ├── mana-utils.ts
 │   │   │   │   ├── pact-utils.ts
 │   │   │   │   ├── result.ts
+│   │   │   │   ├── room-enchantments-utils.ts
 │   │   │   │   ├── room-utils.ts
 │   │   │   │   ├── safe-persist.ts
 │   │   │   │   └── spire-utils.ts