Before this PR, users could not browse or download GGUF models directly from HuggingFace Hub within the UI, nor manage quant-matched draft sidecar files alongside main model downloads.

The existing model manager lacked integration with HuggingFace Hub APIs and did not support coordinating downloads of main quantized models with their corresponding draft sidecar files, resulting in manual, error-prone workflows and missing UI affordances for these operations.

This PR introduces a Discover Models view that fetches and displays HF GGUF models with search, filters, and detailed info, plus download chips showing live states. It extends download logic in common/download.cpp to handle tagged sidecar files (e.g., dflash, mtp) linked to main quant models, enabling automatic and manual draft downloads with synchronized pause/resume/cancel controls. The UI components were updated to show draft sub-lines under main models, and settings were added to toggle Discover integration and filter out unsupported decision models.

When integrating external model repositories into a UI with complex download dependencies, explicitly model and coordinate related file sets (main + sidecars) in both backend download logic and frontend state to maintain consistent user controls and resumable downloads.