Fix Apertus parser: add response block for content with reasoning
When converting reasoning_content to blocks format, add the regular
content as a "response" block after the "thoughts" block. The Apertus
template expects content in blocks format and ignores content.text
when blocks exist.
This fixes the content-with-reasoning scenario where content needles
were not being found because the content was stored in the wrong format.
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>