Add Falcon OCR and OvisOCR2 to the model registry

[davanstrien]

Summary

• add opt-in falcon-ocr (0.3B) and ovis-ocr2 (0.9B) registry entries
• configure both for their documented standard l4x1 launch path
• make ocr-bench run --list-models work without placeholder repo arguments
• document the 16-model registry and a compact Tesseract/Falcon/Ovis selection

The default five-model set is unchanged.

Validation

• uv run pytest tests/ -q — 556 passed
• uv run ruff check src/ tests/
• uv run ty check src/
• verified both uv-script URLs return HTTP 200
• verified --list-models and a two-model --dry-run locally