[Fix] Fix the path resolve issue in windows

[whats2000]

Fix: Fix the path resolve issue in Windows

What this does

This PR fixes a path-resolution issue on Windows by ensuring that pretrained_path is kept as a string rather than converted to a Path object. Using Path() caused backslash/forward-slash inconsistencies, especially when handling HuggingFace repo IDs. The fix ensures consistent forward-slash formatting across platforms.

How it was tested

• Updated eval.py and train.py to avoid using Path() for pretrained_path where forward-slash preservation is required.
• Verified that Windows paths resolve correctly when loading configs.
• Ran local training/eval runs on Windows to ensure no regressions during config loading.

How to checkout & try? (for the reviewer)

To test the behavior locally run a training command that loads a pretrained policy:

lerobot-train --config-path=path/to/config.yaml

[whats2000]

This kinda because the path in the window will use the \\ for path; if we use the path object, this will always make the HuggingFace repo invalid to resolve. So a better way is that we keep them in posix style string to ensure all the paths create by train and resolve by train in posix style!

[DanielBryars]

Ahhh I ran into this too. https://github.com/huggingface/lerobot/issues/2552