feat(examples): add native MCP gateway for Gemma 3 function calling

[junaidaslam2006]

Summary

This PR adds a reference implementation for a Model Context Protocol (MCP) gateway specifically optimized for Gemma 3. It enables local tool-augmented generation (TAG) by bridging Gemma 3 with standardized MCP tool schemas.

Key Technical Contributions

• Native Token Integration: Implements the official Dec 2025 control tokens (<start_function_call>, <start_function_response>) for reliable orchestration.
• Developer Role Support: Correctly utilizes the developer turn logic to trigger Gemma 3's high-reasoning tool-use mode.
• Recursive Tool Loop: Includes a robust execution loop in server.py to handle multi-turn agentic workflows.

Verification

• Verified protocol compliance using @modelcontextprotocol/inspector.
• Tested end-to-end with Gemma 3 (4B) via Ollama.