[Anima] Add img2img pipeline blocks (#13929)
* [Anima] Add img2img pipeline blocks
* [Anima] Address review feedback: remove # Copied from, fold img2img into AnimaAutoBlocks
- Remove incorrect `# Copied from` comment above AnimaImg2ImgSetTimestepsStep
- Delete AnimaImg2ImgAutoBlocks; introduce AnimaAutoDenoiseStep (AutoPipelineBlocks)
and AnimaImg2ImgDenoiseStep (SequentialPipelineBlocks) so img2img lives as a
workflow inside AnimaAutoBlocks, following the z_image pattern
- Update __init__.py, dummy_objects, and docs to remove AnimaImg2ImgAutoBlocks
- Update img2img test to use AnimaAutoBlocks with updated workflow block paths
* Apply style fixes
* [Anima] Refactor img2img: separate VAE encoder step, add AnimaAutoVaeImageEncoderStep
- AnimaImg2ImgVaeEncoderStep now only encodes image → image_latents
- AnimaImg2ImgPrepareLatentsStep handles timestep slicing + noise mixing
- AnimaAutoVaeImageEncoderStep (AutoPipelineBlocks, trigger: image) added to AnimaAutoBlocks
- AnimaAutoDenoiseStep trigger changed from image to image_latents
- Follows z_image pattern (ZImageVaeImageEncoderStep + ZImagePrepareLatentswithImageStep)
* [Anima] Address review: move strength slicing into set_timesteps, add image input step, flatten img2img core denoise
* [Anima] Fix doc-builder style: rewrap docstrings to 119-char width
* [Anima] Address review: rename AnimaAutoDenoiseStep to AnimaAutoCoreDenoiseStep, merge img2img tests into main test file
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Co-authored-by: Álvaro Somoza <asomoza@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
