2.1.6 — Performance Improvement

Fix API response compatibility issues (v0.1.1)

• Make id, object, created fields optional in ChatCompletion
• Make id, object, created, model fields optional in ChatCompletionChunk
• Make Usage fields optional to handle empty usage objects in streaming
• Fix streaming by using httpx send() with stream=True instead of stream context manager

Tested with real API calls:

• Chat completions: working
• Streaming: working
• Embeddings: working
• Tool calling: working