fix titlebar decorations on certain wayland compositors (KDE / KWin)

[yanpla]

No description provided.

[greptile-apps]

Greptile Summary

This change requests client-side window decorations only on Linux so compatible Wayland compositors do not draw an additional native title bar above Starlight’s custom title bar. Linux type-checking passed before and after the change, and the pinned GPUI implementation forwards the client-decoration request while retaining the application title bar.

T-Rex validation blocked

A live Wayland/KWin interaction check could not run because the environment is missing a graphical display service: no WAYLAND_DISPLAY or DISPLAY session is active, and no Wayland compositor is installed. Running the desktop application is also blocked by missing libxkbcommon and libxkbcommon-x11 linker libraries.

Confidence Score: 5/5

T-Rex Logs

What T-Rex did

• I ran cargo check --locked --offline on the parent revision and the revision containing WindowDecorations::Client, and both checks completed successfully.
• I inspected the locked GPUI and gpui-component sources and verified that client decorations are requested by GPUI while the component title bar remains in use.
• I attempted live Wayland interactions but could not perform them due to the absence of an active display service or Wayland compositor and missing libxkbcommon libraries.
• Before: the parent commit’s Linux type-check passed; After: the PR commit’s Linux type-check passed with WindowDecorations::Client enabled.
• Static dependency evidence supports the intended configuration and custom-titlebar compatibility, but it is not a substitute for an actual Wayland window interaction test.

_{Ran code and verified through T-Rex}

_{Reviews (1): Last reviewed commit: "fix titlebar decorations on certain wayl..." | Re-trigger Greptile}