fix: Windows compatibility in from_pretrained

[giteuojeff]

Summary

TribeModel.from_pretrained() fails on Windows with two separate errors. This PR fixes both.

Bug 1 — Invalid repo_id due to Windows path separator

Path("facebook/tribev2") on Windows stringifies to facebook\tribev2 (backslash), which is rejected by hf_hub_download as an invalid repo ID.

Fix: use .as_posix() instead of str() to always produce forward slashes.

Bug 2 — PosixPath cannot be instantiated on Windows

config.yaml was serialised on Linux and contains !!python/object/apply:pathlib.PosixPath YAML tags. Loading it with yaml.UnsafeLoader on Windows raises:

NotImplementedError: cannot instantiate 'PosixPath' on your system

Fix: register a custom YAML constructor directly in yaml_constructors (checked before multi-constructors) that maps both PosixPath and WindowsPath tags to pathlib.Path, which resolves correctly on any platform.

Test

Verified on Windows 11 with Python 3.12, CUDA 12.4, RTX 4050:

from tribev2 import TribeModel
model = TribeModel.from_pretrained("facebook/tribev2", cache_folder="./cache")
# Loads successfully — no errors

Notes for reviewer

• No behaviour change on Linux/macOS; the custom constructor produces the same Path objects as the original code would have.
• WindowsPath and the python/object/new: variants are also covered defensively.

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