QCursor::setPos is a no-op on Wayland, so cursor-follows-focus did
nothing there. Add WaylandCursorWarp (src/plugin/waylandcursorwarp.{h,
cpp}): on Wayland, lock the pointer to the top-level window's wl_surface,
set_cursor_position_hint to the target pane centre (surface-local), commit,
then release — the compositor warps to the hint on unlock (the mechanism
plan9port/acme use). Panes are children of one window = one surface, so
it is a warp within that surface. Handles come from QWaylandApplication +
QPlatformNativeInterface 'surface'. X11 keeps QCursor::setPos.
Build: pointer-constraints client glue generated via ECM and compiled as
a C static lib (kcoreaddons_add_plugin silently drops .c sources); enable
C language in project(); link Qt6::GuiPrivate + wayland-client. All
guarded + a stub when the Wayland bits are absent. 13 ctest suites pass.
eeee28a94a