phsl / new-api

Summary
• Introduced standalone `ModelSelectModal.jsx` for selecting channel models
• Fetch-list now opens modal instead of in-place select, keeping EditChannelModal lean

Modal Features
1. Search bar with `IconSearch`, keyboard clear & mobile full-screen support
2. Tab layout (“New Models” / “Existing Models”) displayed next to title, responsive wrapping
3. Models grouped by vendor via `getModelCategories` and rendered inside always-expanded `Collapse` panels
4. Per-category checkbox in panel extra area for bulk select / deselect
5. Footer checkbox for bulk select of all models in current tab, with real-time counter
6. Empty state uses `IllustrationNoResult` / `IllustrationNoResultDark` for visual consistency
7. Accessible header/footer paddings aligned with Semi UI defaults

Fixes & Improvements
• All indeterminate and full-select states handled correctly
• Consistent “selected X / Y” stats synced with active tab, not global list
• All panels now controlled via `activeKey`, ensuring they remain expanded
• Search, vendor grouping, and responsive layout tested across mobile & desktop

These changes modernise the channel model management workflow and prepare the codebase for upcoming upstream-ratio integration.