fix(mm): disable new model probe API

[psychedelicious]

Summary

There is a subtle change in behaviour with the new model probe API.

Previously, checks for model types was done in a specific order. For example, we did all main model checks before LoRA checks.

With the new API, the order of checks has changed. Check ordering is as follows:

• New API checks are run first, then legacy API checks.
• New API checks categorized by their speed. When we run new API checks, we sort them from fastest to slowest, and run them in that order. This is a performance optimization.

Currently, LoRA and LLaVA models are the only model types with the new API. Checks for them are thus run first.

LoRA checks involve checking the state dict for presence of keys with specific prefixes. We expect these keys to only exist in LoRAs.

It turns out that main models may have some of these keys.

For example, this model has keys that match the LoRA prefix lora_te_: https://civitai.com/models/134442/helloyoung25d

Under the old probe, we'd do the main model checks first and correctly identify this as a main model. But with the new setup, we do the LoRA check first, and those pass. So we import this model as a LoRA.

Thankfully, the old probe still exists. For now, the new probe is fully disabled. It was only called in one spot.

I've also added the example affected model as a test case for the model probe. Right now, this causes the test to fail, and I've marked the test as xfail. CI will pass.

Once we enable the new API again, the xfail will pass, and CI will fail, and we'll be reminded to update the test.

Related Issues / Discussions

n/a

QA Instructions

• The affected main model should correctly import as a main model instead of a LoRA (as it does on main branch right now): https://civitai.com/models/134442/helloyoung25d
• Model types that were on the new API should still import correctly. That includes LoRAs and LLaVA models. I successfully tested:
  • SD1.5 LoRA: https://civitai.com/api/download/models/62833
  • SDXL LoRA: https://civitai.com/models/122359/detail-tweaker-xl?modelVersionId=135867
  • SDXL LoRA (from starter models): https://huggingface.co/RalFinger/alien-style-lora-sdxl/resolve/main/alienzkin-sdxl.safetensors
  • FLUX LoRA (from starter models): black-forest-labs/FLUX.1-Depth-dev-lora::flux1-depth-dev-lora.safetensors
  • LLaVA (from starter models): va-hf/llava-onevision-qwen2-0.5b-ov-hf

Merge Plan

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Checklist

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