Align Qwen parser behavior with Transformers serve by allowing <tool_call> parsing while still in thinking collection.
Changes:
- qwen3vl: detect <tool_call> before </think> in thinking state and transition to tool parsing
- qwen3: same thinking-state tool detection and partial-tag overlap handling
- tests: update qwen3vl thinking/tool interleaving expectations
- tests: add qwen3 cases for tool call before </think> and split <tool_call> streaming