[3pts] Implement turn-based combat loop

[github-actions]

Description

Implement turn-based combat system with CombatEngine class.

Depends on: Character, Player, Enemy, and ICombatStrategy issues

CombatEngine Class

RunCombat(Player player, Enemy enemy)

Returns CombatOutcome with:

• Winner (Character)
• TotalDamageDealt (int)
• ExperienceEarned (int)
• GoldEarned (int)
• TurnCount (int)

Combat Rules

• Player attacks first each turn
• Each character uses their ICombatStrategy.Execute()
• Combat continues until one character dies (Health <= 0)
• Publishes events via GameEventSystem:
  • EnemyDefeatedEvent if player wins
  • PlayerDeathEvent if enemy wins

Requirements

• No UI/console output in CombatEngine
• Pure game logic only
• Combat result encapsulates all outcome data

Acceptance Criteria

• CombatEngine class created
• RunCombat(Player player, Enemy enemy) method implemented
• CombatOutcome class defined with all properties
• Player attacks first each turn
• Uses ICombatStrategy.Execute() for attacks
• Combat continues until one character's Health <= 0
• Publishes EnemyDefeatedEvent on enemy death
• Publishes PlayerDeathEvent on player death
• Returns complete CombatOutcome
• No UI logic in class
• Class documented with XML comments