Fix model download step being skipped during training

[vijaythecoder]

Issue

The training process skips the model download step when the model directory exists but is missing required files (like config.json), causing training to fail later.

Fix

• Added check for config.json file in addition to model directory
• Automatically downloads model if directory or config is missing
• Fixed error handling to use correct ProcessStep enum

Testing

Verified on Apple M4 Pro with 24GB RAM that:

• Empty model directories trigger download
• Directories missing config.json trigger download
• UI correctly shows download progress

This resolves the issue where users manually place model files in the correct directory but training fails due to missing configuration files.

[yingapple]

Thanks for your contribution.

[ScarletttMoon]

Hi @vijaythecoder 👋,

Thank you so much for your contribution to this PR! Your work is really appreciated. If you haven’t already, feel free to join our Discord community here: Discord Invite Link — it's a great place to connect with our team and other contributors, share ideas, and stay up to date with the project! You can find me as @scarlettt_moon there!

Looking forward to connecting! 😊