Content-sized pages like the Search empty state only got the opaque
window background behind their own frame, leaving darker window
material on both sides.
Views without an explicit background sat on the translucent window
material, which picks up a wallpaper tint (bluish in dark mode) and
clashed with views drawing windowBackgroundColor, making the video
info header gradient fade visibly mismatch. Add opaqueWindowBackground()
and apply it centrally in NavigationDestinationHandlerModifier to both
stack roots and pushed destinations, plus VideoInfoView for
presentations outside navigation stacks.
Claude-Session: https://claude.ai/code/session_0154KH8RAVAvm6iVanhmoW8o
