Fix: Cosmos2.5 Video2World frame extraction and add default negative prompt (#13018)
* fix: Extract last frames for conditioning in Cosmos Video2World
* Added default negative prompt
* Apply style fixes
* Added default negative prompt in cosmos2 text2image pipeline
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Co-authored-by: YiYi Xu <yixu310@gmail.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>