llm-provider

# LLM Provider ## Critical 1. **All providers MUST implement the LLMProvider interface** from src/llm/types.ts with three methods: - call(options: LLMCallOptions): Promise<string> — single non-streaming call returning text - stream(options: LLMStreamOptions, callbacks: LLMStreamCallbacks): Promise<void> — streaming call invoking callbacks - listModels?(): Promise<string[]> — optional; list available models from the API 2. **Initialize client in constructor and store defaultModel from config**. Example: `this.client = new YourSDK({ apiKey: config.apiKey })`. Never lazy-initialize on first call — providers are instantiated once and cached in src/llm/index.ts. 3. **For EVERY response in call() and stream(), invoke trackUsage(model, usage)** from src/llm/usage.js before returning/ending. This is mandatory — it captures token metrics for CLI telemetry and cost analysis. If the API doesn't return usage data, estimate via estimateTokens(text), which assumes ~4 chars per token. 4. **Both call() and stream() must respect the model parameter** using pattern: `options.model || this.defaultModel`. Never hardcode model names. Callers supply model overrides via LLMCallOptions.model. 5. **Error handling: catch all errors, preserve error messages unchanged**. The retry logic in src/llm/index.ts handles transient errors (ECONNRESET, socket hang up, 529 overload). For seat-based providers (Cursor, Claude CLI), wrap stderr via parseSeatBasedError() for user-friendly messages. 6....