feat: implement per-enemy damage application (spec §3.2)

- Add applyDamageToRoom() function targeting individual enemies
- Add lowestHPEnemy() helper for focus-fire targeting
- AoE spells distribute damage across all enemies
- Single-target attacks hit lowest HP enemy first
- Refactor processCombatTick spell/equipment/melee/DoT damage to use per-enemy system
- Update golemApplyDamageToRoom in golem-combat pipeline for per-enemy targeting
- Add currentRoom to CombatTickResult and sync through gameStore
- Update combat-actions tests with proper enemy setup for per-enemy tests
- Extract combat-damage.ts module to stay under 400-line limit

docs/dependency-graph.json

@@ -1,6 +1,6 @@
 {
   "_meta": {
-    "generated": "2026-06-03T13:40:50.953Z",
+    "generated": "2026-06-04T09:16:18.073Z",
     "description": "Import dependency graph for src/lib/game. Keys are files, values are arrays of files they import.",
     "usage": "To find what a file affects, search for its path in the VALUES. To find what a file depends on, look at its KEY entry."
   },
@@ -18,6 +18,7 @@
       "constants/prestige.ts",
       "constants/rooms.ts",
       "constants/spells.ts",
+      "data/equipment/equipment-types-data.ts",
       "types/game.ts"
     ],
     "constants/prestige.ts": [
@@ -532,11 +533,17 @@
       "constants.ts",
       "data/guardian-encounters.ts",
       "effects/discipline-effects.ts",
+      "stores/combat-damage.ts",
       "stores/combat-state.types.ts",
+      "stores/dot-runtime.ts",
       "stores/golem-combat-actions.ts",
       "types.ts",
       "utils/index.ts"
     ],
+    "stores/combat-damage.ts": [
+      "stores/combat-state.types.ts",
+      "types.ts"
+    ],
     "stores/combat-descent-actions.ts": [
       "data/guardian-encounters.ts",
       "stores/combat-state.types.ts",
@@ -623,6 +630,12 @@
       "utils/discipline-math.ts",
       "utils/safe-persist.ts"
     ],
+    "stores/dot-runtime.ts": [
+      "constants.ts",
+      "stores/combat-state.types.ts",
+      "types.ts",
+      "types/spells.ts"
+    ],
     "stores/gameActions.ts": [
       "effects/discipline-effects.ts",
       "stores/attunementStore.ts",
@@ -737,6 +750,7 @@
       "stores/uiStore.ts"
     ],
     "stores/pipelines/golem-combat.ts": [
+      "stores/combat-damage.ts",
       "stores/combatStore.ts",
       "stores/golem-combat-actions.ts",
       "stores/manaStore.ts",