* fix: open mobile model/agent panels on tablet-width Capacitor shells and keep composer taps from dismissing the keyboard
* feat: add iPadOS-style split layout to the Capacitor app
- classify the Capacitor shell as mobile in device detection so shared
surfaces (draft starters, panels) stop falling into tablet branches
- add isIPadApp() and useOrientation() helpers
- iPad: persistent full-height sessions sidebar (mobile sessions surface
inline), Changes/Files in a right sidebar with header shortcut toggles
- animate sidebar open/close like the desktop sidebars and add
finger-sized drag-resize with persisted widths
- anchor the overflow menu and the usage/metadata popover next to their
header buttons regardless of open sidebars
* fix: re-anchor metadata popover on layout shifts and untangle sidebar toggle updates
- recompute the iPad metadata popover anchor via a ResizeObserver on its
wrapper so sidebar toggles/resizes while it is open cannot leave it
misplaced
- move the portrait right-panel close out of the setIpadSidebarOpen
updater into plain sequential state updates