Add support for Z.AI's native tool_stream parameter to enable real-time
visibility into model reasoning and tool call execution.
- Automatically inject tool_stream=true for zai/z-ai providers
- Allow disabling via params.tool_stream: false in model config
- Follows existing pattern of OpenRouter and OpenAI wrappers
This enables Z.AI API features described in:
https://docs.z.ai/api-reference#streaming
AI-assisted: Claude (OpenClaw agent) helped write this implementation.
Testing: lightly tested (code review + pattern matching existing wrappers)
Closes#18135
