Build Responsive & Adaptive Layouts

Background: Native [platform] app, [SwiftUI / Compose]. It needs to look
right across: [phones / tablets-iPad / foldables / orientations / Split
View / different text sizes]. Screen in question: [describe].

Use case: Make this layout adapt to size and form factor instead of
assuming one phone screen.

Implementation details:
- iOS: size classes (compact/regular), adaptive stacks, NavigationSplit
  View for iPad, Dynamic Type's effect on layout, landscape and Split
  View/Stage Manager. Android: WindowSizeClass, adaptive layouts for
  tablets, foldable hinge/posture awareness, and configuration changes.
- A strategy for "phone vs large screen" (e.g., single column vs
  list-detail) rather than scattered size checks
- Avoid hard-coded widths; respect safe areas/insets and the keyboard
- Preserve state across rotation/config change

Deliverable: The adaptive layout implementation, the breakpoint/size-class
strategy, the large-screen treatment (list-detail or equivalent),
safe-area/keyboard handling, and previews across the key form factors.