[Bugfix] add Qwen3ReasoningParser

[chaunceyjiang]

The main difference lies here.

vllm/vllm/reasoning/deepseek_r1_reasoning_parser.py

Lines 135 to 137 in 3bbaacb

	else:
	# no </think> in previous or delta, reasoning content continues
	return DeltaMessage(reasoning_content=delta_text)

FIX #17349

[github-actions]

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[chaunceyjiang]

Noticed that another contributor mentioned the PR #17369 before I did, so I'm closing mine.