useCallback captured tripStore at creation time (dep: [routeCalcEnabled]).
If assignments were empty on first render (trip still loading), the callback
would permanently see empty assignments and call setRoute(null) whenever
invoked — e.g. when clicking a place triggers onSelectDay → updateRouteForDay.
Fix: store tripStore in a ref updated on every render so the callback always
reads the latest assignments without needing to be recreated.
41bfcf2f76