feat: implement Transference Channel system for Enchanter attunement

- Add isChanneling, channelSpeedMultiplier, channelDrainRate to CombatState
- Add startChanneling/stopChanneling actions to combat store
- Add transference-channeling discipline with 3 perks (channel-efficiency, channel-power, channel-mastery)
- Add channelIntensity and channelEfficiency to KNOWN_BONUS_STATS
- Create combat-channel.ts with drain + speed multiplier computation
- Apply channel speed multiplier to equipment spells and melee attacks
- Add Channel Transference hold-button UI to SpireCombatPage
- Add compact channel status indicator to SpireCombatControls
- Channel state resets on spire exit, persists across room transitions
- All 1235 existing tests pass

docs/project-structure.txt

@@ -15,7 +15,9 @@ Mana-Loop/
 │   │   ├── attunements/
 │   │   │   ├── enchanter/
 │   │   │   │   ├── systems/
-│   │   │   │   │   └── enchanting-spec.md
+│   │   │   │   │   ├── enchanting-spec.md
+│   │   │   │   │   ├── room-enchantments-spec.md
+│   │   │   │   │   └── transference-channel-spec.md
 │   │   │   │   └── enchanter-spec.md
 │   │   │   ├── fabricator/
 │   │   │   │   ├── systems/
@@ -385,6 +387,8 @@ Mana-Loop/
 │   │   │   │   │   └── pact-ritual.ts
 │   │   │   │   ├── attunementStore.ts
 │   │   │   │   ├── combat-actions.ts
+│   │   │   │   ├── combat-channel-actions.ts
+│   │   │   │   ├── combat-channel.ts
 │   │   │   │   ├── combat-damage.ts
 │   │   │   │   ├── combat-descent-actions.ts
 │   │   │   │   ├── combat-invocation.ts