GUI sets `pad_to_stride` to 16 by default

[gitttt-1234]

Bug description

When training a model through the GUI, the preprocessing configuration sets the pad_to_stride parameter to a default value of 16. However, this value should ideally match the max_stride specified in the model configuration to ensure alignment. Currently, pad_to_stride is only updated to max_stride if it is explicitly set to None here

https://github.com/talmolab/sleap/blob/8228cd24fc4d6585e41bb66d7ddef02c1450b640/sleap/nn/training.py#L1021-L1023

Since the GUI always defaults to 16, this override does not occur—even when a different max_stride is required—potentially leading to inconsistencies during training.

Expected behaviour

pad_to_stride should automatically match max_stride from the model config unless explicitly set.

Actual behaviour

The GUI always sets pad_to_stride to 16, leading to mis-alignment with max_stride.

Your personal set up

• OS:

• Version(s):

• SLEAP installation method (listed here):
  • [ ] Conda from package
  • [ ] Conda from source
  • [ ] pip package
  • [ ] Apple Silicon Macs

Environment packages

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