Model validation

[2cylu2]

This work is for issue #404.

What’s included:

• shared model registry for HARP models
• HARP featured model dropdown now reads from the registry
• pytest-based validation harness
• local PyHARP smoke tests
• first-pass remote validation for HARP dropdown models

Run locally:
python3 -m pip install -r requirements-model-validation.txt
python3 -m pytest tests/model_validation -rA --run-network-validation

For Stability validation:
export HARP_STABILITY_API_KEY=...
python3 -m pytest tests/model_validation -rA --run-network-validation

Current status:

• local example validation works
• some remote dropdown models pass
• several remote Hugging Face models fail with 503, timeouts, or remote runtime errors
• Stability validation reaches the API but currently returns 400 Bad Request
• more provider/model-specific fixes are still needed