Add waypoint route line, snap-to-edit, and halo action menu

Full reticle interaction state machine (idle/snapped/editing), matching
the HTML prototype's mode variable:

- idle: reticle shows "+", tap drops a new waypoint at the map center.
- snapped: after any pan ends, if the map center lands within the
  reticle's on-screen radius (converted to meters at the current
  zoom/latitude) of an existing waypoint, the view auto-recenters onto it
  and the reticle switches to a pencil icon. Tap to enter editing.
- editing: reticle shows a checkmark; panning the map now live-updates the
  target waypoint's position (drag-to-reposition) instead of moving the
  camera "away" from it, and the HaloMenu radial menu appears.

HaloMenu: three ring-wedge hit regions (custom ClipPath/CustomClipper,
angles/radii taken from the prototype's buildRingWedgePath) for
Loiter/Landing/Remove, with Material icons standing in for the
demonstrator's hand-drawn SVGs. Loiter/Landing toggle the waypoint's
action and drop back to snapped; Remove deletes it and returns to idle.

MissionMap now draws a straight white polyline connecting all waypoints
in order (the physically-grounded straight-line + fillet-arc geometry
from doc 3.7/4.6 is still open - this is a straight-line placeholder) plus
a dashed rubber-band preview from the last waypoint to the live map center
while idle.

Note on porting from Leaflet: flutter_map's MapController.move() emits
MapEventMove, not MapEventMoveEnd, so (unlike the prototype's panTo()) the
auto-recenter-on-snap doesn't re-trigger snap detection - no "autoPanning"
guard flag was needed.

Verified with flutter analyze, flutter test (three new tests: halo menu
open/close, remove, loiter toggle - the wedge tap tests had to target the
icon's exact center via tapAt(), since a wedge's bounding-box center falls
outside its actual donut-segment hit area), and a full manual pass on the
Pixel_10a emulator: idle -> add -> snap (auto-recenter confirmed) -> edit
-> drag-reposition (confirmed via re-snap after further panning showing
the moved position, not the original one) -> halo remove -> back to idle,
plus the connecting line rendering correctly between two waypoints set
far apart.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/test/widget_test.dart

@@ -5,8 +5,10 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import 'package:dmc_app/app_mode/app_mode_cubit.dart';
+import 'package:dmc_app/domain/waypoint/flat_waypoint_list.dart';
 import 'package:dmc_app/ui/app_shell.dart';
 import 'package:dmc_app/ui/providers/current_mission_provider.dart';
+import 'package:dmc_app/ui/widgets/halo_menu.dart';
 import 'package:dmc_app/ui/widgets/reticle_button.dart';
 
 Widget _wrap(Widget child) => ProviderScope(
@@ -72,4 +74,92 @@ void main() {
     expect(waypoints.single.lat, closeTo(52.3676, 0.0001));
     expect(waypoints.single.lon, closeTo(4.9041, 0.0001));
   });
+
+  testWidgets(
+      'Zweiter Tap auf den frisch gesetzten Wegpunkt oeffnet das Halo-Menue',
+      (tester) async {
+    final container = ProviderContainer();
+    addTearDown(container.dispose);
+
+    await tester.pumpWidget(
+      UncontrolledProviderScope(
+        container: container,
+        child: BlocProvider(
+          create: (_) => AppModeCubit(),
+          child: const MaterialApp(home: AppShell()),
+        ),
+      ),
+    );
+    await tester.pump();
+
+    // 1. Tap: idle -> snapped (legt Wegpunkt an).
+    await tester.tap(find.byType(ReticleButton));
+    await tester.pump();
+    expect(find.byType(HaloMenu), findsNothing);
+
+    // 2. Tap: snapped -> editing.
+    await tester.tap(find.byType(ReticleButton));
+    await tester.pump();
+    expect(find.byType(HaloMenu), findsOneWidget);
+  });
+
+  testWidgets('Halo-Remove entfernt den Wegpunkt und schliesst das Menue',
+      (tester) async {
+    final container = ProviderContainer();
+    addTearDown(container.dispose);
+
+    await tester.pumpWidget(
+      UncontrolledProviderScope(
+        container: container,
+        child: BlocProvider(
+          create: (_) => AppModeCubit(),
+          child: const MaterialApp(home: AppShell()),
+        ),
+      ),
+    );
+    await tester.pump();
+
+    await tester.tap(find.byType(ReticleButton)); // idle -> snapped
+    await tester.pump();
+    await tester.tap(find.byType(ReticleButton)); // snapped -> editing
+    await tester.pump();
+
+    // Die Wedge-Bounding-Box-Mitte liegt ausserhalb der Keilform (Donut-
+    // Segment) - stattdessen exakt auf das (nicht hit-testbare) Icon tippen,
+    // das per Konstruktion innerhalb des Keils sitzt.
+    await tester.tapAt(tester.getCenter(find.byIcon(Icons.remove)));
+    await tester.pump();
+
+    expect(container.read(currentMissionProvider), isEmpty);
+    expect(find.byType(HaloMenu), findsNothing);
+  });
+
+  testWidgets('Halo-Loiter setzt die Execute-Aktion und schliesst das Menue',
+      (tester) async {
+    final container = ProviderContainer();
+    addTearDown(container.dispose);
+
+    await tester.pumpWidget(
+      UncontrolledProviderScope(
+        container: container,
+        child: BlocProvider(
+          create: (_) => AppModeCubit(),
+          child: const MaterialApp(home: AppShell()),
+        ),
+      ),
+    );
+    await tester.pump();
+
+    await tester.tap(find.byType(ReticleButton)); // idle -> snapped
+    await tester.pump();
+    await tester.tap(find.byType(ReticleButton)); // snapped -> editing
+    await tester.pump();
+
+    await tester.tapAt(tester.getCenter(find.byIcon(Icons.loop)));
+    await tester.pump();
+
+    final waypoints = container.read(currentMissionProvider);
+    expect(waypoints.single.action, WaypointAction.loiter);
+    expect(find.byType(HaloMenu), findsNothing);
+  });
 }