[arzafran]

Summary

• keep the window-sized shell on a stable AppKit visual-effect backdrop
• restrict native Liquid Glass to the constant-height chrome and bounded controls
• remove the tab-strip-wide glass batching container and update surface regression coverage

Root cause

Window- and strip-sized native refractive surfaces could outgrow a reliable Retina backing-texture budget, causing AppKit to stretch or drop texture tiles while moving or resizing large windows.

Impact

Large windows keep a stable shell while retaining native Liquid Glass on the toolbar, tab pills, and overlays. The macOS 12–25 fallback behavior remains supported.

Validation

• cmake --build build
• ctest --test-dir build --output-on-failure -R 'native_glass_surfaces|appearance_persistence'
• live AppKit smoke: launch, Screenshot Mode hide/restore, accessibility-tree restoration
• visual inspection at a 1880×1030 Retina window footprint
• git diff --check