fix(gguf): honor ComfyUI's comfy.gguf.orig_shape metadata

[Pfannkuchensack]

Summary

Kind of change: fix (backend, GGUF model loading).

Why: Certain ComfyUI-produced GGUF checkpoints install fine but fail at generation with a weight shape mismatch, e.g. for a Krea-2 Q4_K_M checkpoint:

size mismatch for img_in.weight: copying a param with shape torch.Size([1536, 256])
from checkpoint, the shape in current model is torch.Size([6144, 64])

ComfyUI's GGUF converter can only quantize 2-D tensors, so it reshapes any tensor whose native shape the quantizer rejects and records the native shape in a comfy.gguf.orig_shape.<tensor name> KV entry. gguf_sd_loader ignored those entries and used the stored shape instead, so load_state_dict saw a wrongly-shaped tensor.

The affected file's header shows exactly this — note that both shapes have the same element count, so it is purely a reshape:

comfy.gguf.orig_shape.first.weight  [6144, 64]
first.weight                        [256, 1536]  F32

This is not Krea-2 specific; other Krea-2 GGUFs load only because their conversion did not have to reshape this tensor.

How: gguf_sd_loader now reads the comfy.gguf.orig_shape.* metadata and uses the declared native shape for the GGMLTensor. An entry whose element count does not match the stored tensor raises with an explicit message rather than producing a silently wrong view; a malformed entry is logged and ignored.

Related Issues / Discussions

Closes #9537

QA Instructions

Unit tests:

pytest tests/backend/quantization/gguf/test_loaders.py

They cover all three paths: metadata present (shape is applied), metadata absent (unchanged behaviour), metadata inconsistent (raises).

Manual, with the checkpoint from #9537 (Krea-2 SAT-IOR v2 Q4_K_M GGUF from CivitAI):

1. Install the GGUF via the model manager — it is probed as main / krea-2 / gguf_quantized.
2. Run a text-to-image generation with it (a standalone Qwen3-VL encoder and the Qwen-Image VAE, since a single-file checkpoint bundles neither).
3. Before this change: generation fails with the size mismatch above. After: load_state_dict reports no missing or unexpected keys, and generation completes with a coherent image (verified at 512x512, 4 steps).

Also worth a quick regression check that an unaffected GGUF (e.g. an existing FLUX or Krea-2 GGUF without comfy.gguf.orig_shape keys) still loads — those files take the unchanged code path.

Merge Plan

Nothing special — self-contained backend change, no schema or frontend impact.

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• ❗Changes to a redux slice have a corresponding migration
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)