feat: add RegionE support for Qwen-Image-Edit.

[BurnWan]

Description

This PR adds RegionE support for Qwen-Image-Edit Plus and integrates it with the DiT cache framework.

Main changes include:

• Add RegionE-aware denoising flow in /export/home/wanben.burn/xllm/xllm/models/dit/pipelines/pipeline_qwenimage_edit_plus.h.

  • Prepare RegionE inference state before the denoising loop.
  • Build per-step RegionE plans and inputs.
  • Support partial latent execution, cached velocity reuse, direct unedited-region updates, and scatter/reduce back to full latents.
  • Preserve the original scheduler path when RegionE is disabled.

• Add RegionE-aware transformer behavior in /export/home/wanben.burn/xllm/xllm/models/dit/transformers/transformer_qwen_image.h.

  • Disable DiT SP communication overlap for RegionE.
  • Process RegionE image K/V cache inside double-stream attention.
  • Adjust image RoPE for partial-query/full-KV attention layouts.
  • Add RegionE block-level state setup and image KV prefetching.

These changes are needed because RegionE changes the execution granularity from full-image latent updates to region-aware/partial latent updates, which requires coordination between the pipeline scheduler loop, transformer attention, KV cache handling, RoPE alignment, and sequence-parallel synchronization.

Related Issues

N/A

Change Type

• Bug fix
• New feature
• Performance improvement
• Refactor
• Documentation
• Test
• Build or CI

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