ui: provide touch accessible model selection UI (#24604)
* ui : add model selector storybook stories
Covers list, favorites, single-model, all status states
(loading/loaded/sleeping/failed/idle), and selection states.
* ui : improve model selector mobile UX with hover media queries
Use @media (hover:none) to show action buttons directly on touch
devices and color-code them by model status (amber=sleeping,
green=loaded, muted=idle). Status dots hidden on touch. Desktop
hover behavior unchanged.
