Add `packages/app/src/constants/platform.ts` with canonical gates
(isWeb, isNative, getIsElectron) and refactor all ~100 ad-hoc
Platform.OS checks across 69 files to use shared imports.
Fix sidebar hover crash on native (onPointerEnter → onHoverIn),
fix tooltip to use breakpoint instead of platform detection, make
sidebar action buttons always visible on native where hover doesn't
work, and document the platform gating decision matrix in CLAUDE.md.
Replace the stateful TitlebarDragRegion (hooks, ResizeObserver, IPC,
fullscreen tracking) with a pure static component — matching VS Code's
titlebar-drag-region exactly: position absolute, full size, no z-index,
no pointer-events, no state, no event listeners.
Remove TitlebarNoDragContent entirely — VS Code doesn't wrap content in
no-drag; interactive elements get no-drag from the global CSS backstop
in index.html.
Add drag regions to all header surfaces:
- ScreenHeader (sessions, workspace header)
- Left sidebar (traffic light area + header)
- Split container pane tabs
- Explorer sidebar header (Changes/Files tabs)
Fix workspace header empty space not draggable by changing
headerTitleContainer from flex: 1 to flexShrink: 1.
Mohamed Boudra