The tray Selected an exit node with append=false, which the RouteSelector
treats as "drop the whole current selection" (default-on semantics), so
enabling an exit node also turned off every non-exit routed network the
user had on. Send append=true instead and let the daemon's SelectNetworks
handler deselect only the sibling exit nodes — matching the frontend's
toggleExitNode, which already used append=true.
Add a RouteSelector regression test covering the handler sequence.
0853cec437