Replaces useTrafficLightPadding with a role-based useWindowControlsPadding
hook that absorbs all layout-conditional logic (sidebar state, focus mode,
explorer state). Consumers no longer make platform or layout decisions —
they just apply the resolved padding values.
Fixes Windows title bar overlay buttons overlapping source control icons
when the left sidebar is open, and right padding not shifting to the
explorer sidebar header when it's open.
Also fixes borderless header using borderBottomWidth:0 (layout shift)
instead of transparent, and double-click-to-maximize bounce on the
open project screen caused by nested drag handlers.
Sidebar shows a card with "No projects yet" and an Add project ghost
button. Sessions screen shows "No sessions yet" with a ghost Back
button. Open-project screen uses MenuHeader borderless, shared Button,
and shows introductory text when no projects exist.
Use titleBarStyle: 'hidden' on all platforms. On Windows/Linux, enable
titleBarOverlay with dark theme colors for native min/max/close buttons.
Extend useTrafficLightPadding to return side ('left'|'right'|null) so
consumers apply padding on the correct side per platform.
Mohamed Boudra