Refine UI alignment, fix dark mode toggle, and improve model selection logic

fix: restore working copy/save buttons in dark mode and elevate model prompt styling

feat: directive prompts per model, BrainCircuit icon, info tooltip light mode fix

fix: dynamic compression ratio, CUD badge in navbar, slate-300 borders, matched output text size

fix: complete light mode - dataset preview, stats cards, model names, buttons all readable

feat: UI overhaul - light mode, larger text, live ROUGE metrics, dataset loader, speed improvements

Final cleanup for alignment and model selection

Refine UI and fix model selection bugs