Add VS Code local MLX model example

[ahnafyy]

Summary

Add a new vscode_lm example that serves a local MLX coding model through an OpenAI-compatible chat endpoint for use with VS Code language model integration.

What changed

• add a new vscode_lm/server.py example built on mlx-lm
• expose GET /health, GET /v1/models, and POST /v1/chat/completions
• add basic prompt-mediated tool-calling support for agent-style requests
• document the VS Code setup flow in vscode_lm/README.md
• add a sample chatLanguageModels.example.json config
• link the new example from the top-level README.md
• ignore the local virtualenv created for this example in .gitignore

Notes

• the example defaults to no-auth local usage for simpler setup
• the default model is mlx-community/Qwen2.5-Coder-1.5B-Instruct-4bit to fit local disk and memory constraints better than the 7B model
• the example was validated end-to-end locally with /health, /v1/models, and a real /v1/chat/completions request

Validation

• start server from the local Python 3.12 virtualenv
• verify GET /health
• verify GET /v1/models
• verify POST /v1/chat/completions returns a completion without auth