Add OpenAI-compatible local agent backend

[ddonofrio]

Title

Add OpenAI-Compatible Local Agent Backend

Description

What changed

Adds a local backend to SwarmForge for communicating with OpenAI-compatible local servers such as LM Studio and llama.cpp.

Includes:

• Configurable host, port, model, and API key.
• Automatic model discovery through /v1/models.
• Chat completion support through /v1/chat/completions.
• Tools for listing, reading, and writing project files.
• Project command execution with user confirmation.
• Integration of the local backend into the SwarmForge launcher.
• Configuration template and documentation.

Validation

• Python syntax validated.
• Tested against a simulated HTTP server.
• Tool-calling loop tested.
• git diff --check passes.

The backend uses only Python’s standard library and requires no additional Python packages.