* Studio: render thinking blocks for safetensors inference with prefilled <think> templates
Reasoning templates like Qwen3.6 end the generation prompt with an open
<think> tag. skip_prompt streaming drops it, so the frontend never sees
the opening tag and shows reasoning as plain text. Detect the prefill
and re-emit it at the start of the stream on the transformers and MLX
paths. Also stop stripping think tags in _clean_generated_text when a
tokenizer marks them special.
* Studio: guard think re-emit for special close tags, yield prefill early
Address review feedback:
- Guard: skip re-emitting the open <think> when the tokenizer marks </think>
as a special token, since skip_special_tokens would strip the model's close
tag and leave an unclosed block that swallows the answer. Falls back to
plain text (pre-fix behaviour) for those tokenizers.
- Yield the prefilled <think> before the first token so the thinking block
renders during prompt prefill instead of after the first generated token.
- Drop the now-unnecessary _clean_generated_text think-tag exemption; the
guard handles the special-token case at the source.
No mainstream reasoning model (Qwen3.6, Qwen3, DeepSeek-R1, QwQ, GLM-4.6)
marks think tags special, so behaviour is unchanged for them.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Lyxot <longyixing331@gmail.com>
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