On shade, the client scene node was lowered and disabled, and the
frame_buf scene node was disabled. On unshade, the frame_buf node
was not re-enabled, and the client node was enabled but remained
behind the frame (at bottom of Z-order from stacking_lower).
Fix: re-enable frame_buf node when show_resizebar is true, and
raise the client scene node to top on window_map so it's above
the frame background.
- Add selection_acquire, selection_release, platform_init to
W_ViewBackend struct (were used but not declared).
- Add lookup_string to W_FontBackend struct (same issue).
- Guard selection_acquire call with NULL check in selection.c.
- Remove pixman_image_unref in wl_frame_configure resize path —
wlroots manages the buffer lifecycle via scene refcounting.
LSan confirms no leak.
- Remove #include of wmspec.c/xdnd.c/xmodifier.c from x11_backend.c
— they are already compiled as standalone objects, causing
multiple-definition linker errors on clean builds.