Previously, `unmap_surface` automatically pushed all unmapped windows
into the `pending_windows` list. This behavior is correct for X11
windows (which may be remapped) but incorrect for Wayland `toplevel_destroyed`
events, where the role is permanently gone.
This caused issues with clients like Telegram that reuse `wl_surface`s.
Because the destroyed toplevel remained in `pending_windows`, a
subsequent cleanup commit (e.g., null buffer) triggered a configure
event. This prematurely marked the surface as `configured` in the
shell state.
Consequently, when the client attached a new `xdg_toplevel` role,
the compositor skipped the mandatory initial configure event (assuming
it was already done), causing the window to never appear.
This refactors `unmap_surface` to return `Option<PendingWindow>`
instead of mutating global state.
- XWayland: Explicitly saves the pending window (behavior preserved).
- XDG Shell: Drops the pending window, preventing ghost state interactions.
Fixes#1816
15b6b678c1