[BE-1] Implement TryHit Handler with Hit Detection Logic

[sarkarshuvojit]

Parent Epic

#22

Description

Implement the TryHit WebSocket handler that allows players to attempt hitting cells on opponent boards.

Requirements

• Handler receives: targetSessionID, x, y coordinates
• Validate it's the player's turn
• Validate target is a valid opponent
• Validate coordinates are within bounds (0-9)
• Validate cell hasn't been hit before
• Detect hit or miss based on opponent's ship positions
• Update opponent's board state (HIT or MISS)
• Broadcast result to all players in room

Events

• Inbound: TRY_HIT (already defined)
• Outbound: HIT_ATTEMPTED / BOARD_UPDATED

Files to Modify

• internal/api/handlers/ - New handler
• internal/api/events/ - Payload types if needed
• internal/game/ - Hit detection logic

Unit Tests

• Hit detection on ship cell returns HIT
• Hit detection on empty cell returns MISS
• Already hit cell is rejected
• Out of bounds coordinates rejected

Acceptance Criteria

• TryHit handler implemented
• Hit/Miss detection working
• Board state updated correctly
• Unit tests passing