Constant FLOATING_SURFACE_PROTOCOL_VERSION 

pub const FLOATING_SURFACE_PROTOCOL_VERSION: u16 = 5; // 5u16

Version of the app ↔ shell wire contract on the shell-ui channel: floating-surface lifecycle and the window’s appearance. Geometry is encoded as plain logical-pixel arrays rather than renderer types so sandbox services, Wayland protocol shims, and test transports can all carry the same messages.