feat(combat): add the Slice 0.6 action and event-type enum members

apps/api/src/combat/combat-action.enum.ts

@@ -1,6 +1,7 @@
-// Only ATTACK is implemented in Slice 0.3. Future slices add HEAVY_STRIKE,
-// SHIELD_BASH, DEFEND, POTION, FLEE as real members with their own
-// CombatEngineService cases — do not add them here until their behavior ships.
 export enum CombatAction {
   ATTACK = 'ATTACK',
+  HEAVY_STRIKE = 'HEAVY_STRIKE',
+  SHIELD_BASH = 'SHIELD_BASH',
+  DEFEND = 'DEFEND',
+  POTION = 'POTION',
 }