Feature Request

Add LM Studio as a local model provider alongside Ollama

Motivation

LM Studio demonstrates significant performance advantages over Ollama with the same models:

• 26-30% higher tokens/second on identical hardware
• Provides detailed performance metrics (tokens/sec, TTFT) in API responses
• GPU offloading enables partial acceleration when models exceed VRAM
• OpenAI-compatible API at http://localhost:1234/v1/*

For local agent deployments, this performance difference is crucial for real-time responsiveness.

Proposal

Add rig::providers::lmstudio module implementing the CompletionModel trait:

// rig-core/src/providers/lmstudio/mod.rs
pub struct Client {
    base_url: String,
    http_client: reqwest::Client,
}

impl Client {
    pub fn from_default() -> Self {
        Self::new("http://localhost:1234/v1")
    }
}

The provider would:

1. Use OpenAI-compatible endpoints (already proven in Rig)
2. Support streaming responses
3. Expose LM Studio's performance metrics in responses