- anthropic: previously ignored the stream flag entirely (always non-stream).
  Add _handle_streaming_request converting Anthropic SSE events into
  OpenAI-compatible chunks (text deltas, tool_use/input_json deltas, usage).
- ollama: previously hard-coded stream=False. Add incremental streaming over
  /api/generate yielding OpenAI chunks.
- google: was buffering the entire response before yielding. Stream chunks
  incrementally as they arrive when no tools are requested (the common case);
  keep the buffer-and-parse path only when tools are present, since the
  text-encoded tool-call detection needs the complete response.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>