fix(map): the location button follows the viewport instead of the mount

Both renderers read window.innerWidth once while rendering, so the button
that turns GPS on was decided by the width the map happened to see when it
mounted: a phone turned sideways crosses the 768px cut and kept whatever it
had, and turning back did not bring it home either. Both now use the same
useIsPhone the shell switches on. The test stub for matchMedia answers width
queries from window.innerWidth and re-evaluates on a resize, so a breakpoint
can be driven from a test the way the browser drives it.

client/src/components/Map/MapViewGL.tsx

@@ -22,6 +22,7 @@ import { visibleRouteReservations } from '../../utils/reservationRoutes'
 import { safeHexColor } from '../../utils/safeColor'
 import { MAPBOX_DEFAULT_STYLE, styleForActiveProvider, basemapLanguage, type GlMapProvider } from './glProviders'
 import LocationButton from './LocationButton'
+import { useIsPhone } from '../../mobile/useIsPhone'
 import { useGeolocation } from '../../hooks/useGeolocation'
 import type { Day, Place, Reservation, RouteVia } from '../../types'
 import type { MapHoverInfo } from './mapHover'
@@ -1159,6 +1160,12 @@ export function MapViewGL({
   const onMapReadyRef = useRef(onMapReady)
   onMapReadyRef.current = onMapReady
   const { position: userPosition, mode: trackingMode, error: trackingError, errorCode: trackingErrorCode, cycleMode: cycleTrackingMode, setMode: setTrackingMode } = useGeolocation()
+  // Desktop browsers only get IP-based geolocation (city-level accuracy), so
+  // the location button would be misleading; the phone, where real GPS lives,
+  // keeps it. Read here with the other hooks rather than beside the button:
+  // the tokenless branch below returns early, and a hook after it runs on some
+  // renders and not others.
+  const isMobile = useIsPhone()
   const onClickRefs = useRef({ marker: onMarkerClick, map: onMapClick, context: onMapContextMenu })
   onClickRefs.current.marker = onMarkerClick
   onClickRefs.current.map = onMapClick
@@ -2382,9 +2389,6 @@ export function MapViewGL({
     )
   }
 
-  // Desktop browsers only get IP-based geolocation (city-level accuracy),
-  // so the button would be misleading. Mobile, where real GPS lives, keeps it.
-  const isMobile = typeof window !== 'undefined' && window.innerWidth < 768
   // When the day-detail panel is open it slides up over the map (bottom: navh+20,
   // height var(--day-panel-h)) and covers the button's band, so lift the button
   // above it; otherwise keep the plain bottom-nav offset. #1348