FB-01: fix ambient GPS's first fix not correcting the initial zoom-2

Emulator verification caught a real bug the widget tests missed: the
shell background map builds before any location fix has resolved, so
ambientPosition starts null and the initial camera locks at zoom 2.
The first fix to arrive only re-centered (preserving that stale zoom
forever) instead of also jumping to ambientZoom.

lib/src/ui/components/ride_map.dart

@@ -153,10 +153,19 @@ class _RideMapState extends State<RideMap> with WidgetsBindingObserver {
     } else if (widget.ambientPosition != null &&
         widget.ambientPosition != old.ambientPosition) {
       // FB-01: no recorded path yet -- chase the ambient GPS fix instead, the same way
-      // a recording is chased above.
+      // a recording is chased above. The *first* fix has to also correct the zoom, not
+      // just the center: the very first build (before any fix has arrived) has no
+      // ambient position yet either, so `bounds == null` locks the initial camera at
+      // zoom 2 -- without this, every later fix would re-center at that same
+      // never-corrected zoom 2 forever, since a plain re-center only ever preserves
+      // whatever zoom the map is already at.
+      final isFirstFix = old.ambientPosition == null;
       WidgetsBinding.instance.addPostFrameCallback((_) {
         if (!mounted || !_following) return;
-        _controller.move(widget.ambientPosition!, _controller.camera.zoom);
+        _controller.move(
+          widget.ambientPosition!,
+          isFirstFix ? ambientZoom : _controller.camera.zoom,
+        );
       });
     }
   }

test/ride_map_test.dart

@@ -250,6 +250,45 @@ void main() {
       expect(center.longitude, closeTo(fix2.longitude, 1e-9));
     });
 
+    testWidgets('the first ambient fix to arrive after construction corrects the '
+        'zoom, not just the center -- a plain re-center would otherwise leave the '
+        'map at the initial zoom-2 forever', (tester) async {
+      // Reproduces a real device bug found in emulator verification: the shell
+      // background map builds before any location permission/fix has resolved, so
+      // `ambientPosition` starts null and the initial camera locks at zoom 2 (the
+      // `bounds == null` fallback). The first fix to actually arrive must jump to
+      // `ambientZoom`, not just re-center at whatever zoom the map already happens
+      // to be sitting at.
+      const fix = ll.LatLng(51.0, -114.0);
+
+      Widget build(ll.LatLng? ambient) => MaterialApp(
+            theme: ripprTheme(),
+            home: Scaffold(
+              body: RideMap(
+                points: const [],
+                segments: const [],
+                showEmptyLabel: false,
+                follow: true,
+                ambientPosition: ambient,
+              ),
+            ),
+          );
+
+      await tester.pumpWidget(build(null));
+      await tester.pump();
+
+      var map = tester.widget<FlutterMap>(find.byType(FlutterMap));
+      expect(map.mapController!.camera.zoom, 2);
+
+      await tester.pumpWidget(build(fix));
+      await tester.pump();
+
+      map = tester.widget<FlutterMap>(find.byType(FlutterMap));
+      expect(map.mapController!.camera.zoom, ambientZoom);
+      expect(map.mapController!.camera.center.latitude, closeTo(fix.latitude, 1e-9));
+      expect(map.mapController!.camera.center.longitude, closeTo(fix.longitude, 1e-9));
+    });
+
     testWidgets('a manual pan cancels ambient following the same way it cancels '
         'recording-follow', (tester) async {
       const fix1 = ll.LatLng(51.0, -114.0);