Fix: add .onnx to supported_pt_extensions to allow loading ONNX models

[aoright]

Resolves #14676. Many custom nodes (e.g. WanAnimatePreprocess) load pre-trained ONNX models and look up files using ComfyUI's model path APIs. Since .onnx was missing from supported_pt_extensions, these files were silently ignored and failed to load. This PR adds .onnx to supported_pt_extensions and adds a corresponding unit test to ensure stability.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 7851410 and 79641dc.

📒 Files selected for processing (2)

• folder_paths.py
• tests-unit/folder_paths_test/misc_test.py

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📝 Walkthrough

Walkthrough

The .onnx extension is added to the supported_pt_extensions set in folder_paths.py. A corresponding unit test is added in tests-unit/folder_paths_test/misc_test.py that asserts .onnx is present in supported_pt_extensions.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states the main change: adding .onnx support to load ONNX models.
Description check	✅ Passed	The description is directly related to the PR and accurately explains the .onnx support fix and test.
Linked Issues check	✅ Passed	The changes satisfy #14676 by adding .onnx to supported_pt_extensions and verifying it with a unit test.
Out of Scope Changes check	✅ Passed	The PR only includes the requested extension update and a matching test, with no obvious unrelated changes.

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[Kosinkadink]

This seems fine to me, I'll make sure other folks are onboard first