Mobile (≤480px):
- Hide Side Panel, Floating, Full Screen buttons
- Show Split button (50vh vertical split, CV visible above)
- Compact mode: 55vh max bottom sheet
- Force desktop modes to compact if somehow activated
- Disable tooltips on mobile (overflow prevention)
- Tighter header padding
Desktop (>480px):
- Split button hidden, all modes available as before
Tests: 85-chat-mobile.test.mjs — 79 assertions across
iPhone SE (320x568), iPhone 14 (393x852), iPhone 14 Pro Max (430x932),
plus desktop sanity check
juanatsap