feat: implement regular enemy defenses — armor, barrier, dodge (spec §5.2)

- Add applyEnemyDefenses() pipeline: dodge → barrier → armor for ALL enemies
- Add speed room + agile additive dodge (capped at 0.75, spec §4.5)
- Add mage barrier recharge per tick (spec §5.2)
- Add effectiveArmor support for armor_corrode debuff compatibility
- Pass enemy defense context via closure (no signature changes to onDamageDealt)
- Add 16 regression tests for defense mechanics
- All 921 tests pass (45 test files)

docs/project-structure.txt

@@ -194,6 +194,7 @@ Mana-Loop/
 │   │   │   │   ├── discipline-prerequisites.test.ts
 │   │   │   │   ├── discipline-reactivate-bug.test.ts
 │   │   │   │   ├── enemy-barrier-utils.test.ts
+│   │   │   │   ├── enemy-defenses.test.ts
 │   │   │   │   ├── enemy-generator.test.ts
 │   │   │   │   ├── enemy-utils.test.ts
 │   │   │   │   ├── floor-utils.test.ts