Implement robust GABP mirroring with connection retry logic

[Copilot]

This PR implements the "Future Enhancement" mentioned in stdio_server.go line 668, adding robust GABP (Game Agent Bridge Protocol) mirroring that works even when game mods are still starting up.

Problem

The existing code created bridge configurations and started games, but never actually connected to GABP servers or set up tool mirroring. The comment indicated this was a future enhancement that needed to handle the case where "the other end is still starting" - meaning game mods might take time to initialize their GABP servers.

Solution

🔄 Background Connection with Retry Logic

• Added establishGABPConnection() method that runs in background after game startup
• Implements exponential backoff (100ms to 5s) with jitter to handle slow-starting game mods
• Connection failures don't block game startup - games work normally with or without GABP support

🔧 Automatic Tool Mirroring

• When GABP connection succeeds, game tools are automatically mirrored to MCP
• Tools get game-specific prefixes (e.g., minecraft.inventory.get) to prevent conflicts
• Original tool functionality is preserved while enabling multi-game support

📡 Real-time AI Agent Notifications

• Sends tools/list_changed notifications when new tools become available
• AI agents can dynamically discover new capabilities via existing games.tools command
• No polling required - agents are notified immediately when tool sets expand

🛡️ Proper Resource Management

• Added Close() method to gabp.Client for graceful connection cleanup
• Game-specific tools and resources are automatically cleaned up when games stop
• Updated cleanup logic in stopGame() and checkGameStatus() methods

Workflow

1. Game starts → Bridge config created, game process launched
2. Background connection → GABP client attempts connection with retry logic
3. On success → Tools mirrored, resources exposed, notifications sent to AI agents
4. Dynamic discovery → AI agents automatically learn about new game capabilities
5. On game stop → GABP connections closed, game-specific tools cleaned up

Testing

• Added comprehensive test suite covering tool mirroring, cleanup, and connection retry logic
• All existing tests continue to pass
• Integration tests verify the complete workflow from connection to cleanup

This implementation fulfills the original enhancement goal of making GABP mirroring robust and automatic, ensuring AI agents are immediately aware when game tool sets expand dynamically.

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