Restore robust desktop density

[hamzamerzic]

Summary

Restore the owner-selected 90% density for desktop web while keeping tablet and phone layouts at native scale. The change centralizes the real browser boundary between painted client coordinates and zoomed layout coordinates so compact desktop chrome no longer compromises dragging, menus, scrolling, viewport fitting, image gestures, or theme transitions.

Changes

• restore document-level desktop density at the existing 1024px breakpoint
• add one small layout-space module and route custom client-to-layout geometry through it
• keep mini-app frames native and preserve physical gesture thresholds
• cover desktop, tablet, and phone shell bounds plus physical divider travel
• document the coordinate-space contract and remove superseded native-only helpers

This deliberately revisits #480. That PR correctly removed an incomplete zoom implementation whose callers mixed painted and layout coordinates; this version restores the requested density together with a reviewed, single conversion boundary and browser-level regressions for the interactions that previously broke.

Testing

• 2,336 frontend library tests
• 79 frontend hook tests
• lint (44/47 warning ratchet)
• production and offline/PWA builds
• git diff --check

Pre-ship review: the coordinate bridge exposes only captured space plus client point/delta conversion; unused inverse and rectangle APIs were removed, gesture snapshots reuse one captured space, and source-reading assertions were reduced in favor of unit and browser behavior.