Fix route preview acceleration and braking layers

lib/features/map/map_screen.dart

@@ -33,8 +33,6 @@ class _MapScreenState extends ConsumerState<MapScreen> {
   bool _showHardBraking = true;
   bool _showCornering = true;
 
-  // These are intentionally derived from the already-persisted telemetry.
-  // They do not alter the frozen telemetry acquisition/fusion pipeline.
   static const double _hardAccelThresholdG = 0.35;
   static const double _hardBrakingThresholdG = -0.35;
   static const Duration _eventMergeWindow = Duration(milliseconds: 1500);
@@ -133,8 +131,6 @@ class _MapScreenState extends ConsumerState<MapScreen> {
     return markers;
   }
 
-  // Build map events directly from persisted longitudinal G when RideEvents are
-  // absent/incomplete. Existing RideEvents remain untouched and are still shown.
   List<AppMapMarker> _buildTelemetryEventMarkers(List<TelemetrySample> samples) {
     final gps = samples.where((s) =>
         s.latitude != null && s.longitude != null &&
@@ -248,13 +244,24 @@ class _MapScreenState extends ConsumerState<MapScreen> {
       );
 
   List<AppPolyline> _buildPolylines() {
-    if (_routePoints.isEmpty || !_showRoute) return [];
+    if (_routePoints.isEmpty) return [];
-    if (!_showSpeedHeatmap) {
+
-      return [AppPolyline(id: 'history_route', points: _routePoints, color: const Color(0xFF00E5FF), width: 4.5)];
-    }
     final polylines = <AppPolyline>[];
-    final validSamples = _telemetrySamples.where((t) => t.latitude != null && t.longitude != null).toList();
+    if (_showRoute) {
-    if (validSamples.isEmpty) return [];
+      polylines.add(AppPolyline(
+        id: 'history_route',
+        points: _routePoints,
+        color: const Color(0xFF00E5FF),
+        width: 4.5,
+      ));
+    }
+
+    final validSamples = _telemetrySamples
+        .where((t) => t.latitude != null && t.longitude != null)
+        .toList();
+    if (validSamples.isEmpty) return polylines;
+
+    if (_showSpeedHeatmap) {
       final step = (validSamples.length / 1500).ceil().clamp(1, 10);
       List<AppLatLng> currentSegment = [];
       Color currentColor = _getSpeedColor(validSamples.first.speed ?? 0.0);
@@ -274,6 +281,60 @@ class _MapScreenState extends ConsumerState<MapScreen> {
       if (currentSegment.length > 1) {
         polylines.add(AppPolyline(id: 'speed_seg_${polylines.length}', points: currentSegment, color: currentColor, width: 5.0));
       }
+    }
+
+    if (_showHardAccel) {
+      polylines.addAll(_buildLongitudinalEventPolylines(
+        validSamples,
+        predicate: (g) => g >= _hardAccelThresholdG,
+        idPrefix: 'accel_layer',
+        color: const Color(0xFF76FF03),
+      ));
+    }
+    if (_showHardBraking) {
+      polylines.addAll(_buildLongitudinalEventPolylines(
+        validSamples,
+        predicate: (g) => g <= _hardBrakingThresholdG,
+        idPrefix: 'braking_layer',
+        color: const Color(0xFFFF5252),
+      ));
+    }
+
+    return polylines;
+  }
+
+  List<AppPolyline> _buildLongitudinalEventPolylines(
+    List<TelemetrySample> samples, {
+    required bool Function(double g) predicate,
+    required String idPrefix,
+    required Color color,
+  }) {
+    final polylines = <AppPolyline>[];
+    List<AppLatLng> segment = [];
+    var segmentIndex = 0;
+
+    void flush() {
+      if (segment.length >= 2) {
+        polylines.add(AppPolyline(
+          id: '${idPrefix}_$segmentIndex',
+          points: List<AppLatLng>.from(segment),
+          color: color,
+          width: 7.0,
+        ));
+        segmentIndex++;
+      }
+      segment = [];
+    }
+
+    for (final sample in samples) {
+      final g = sample.longitudinalG ?? sample.accelX;
+      if (g != null && g.isFinite && predicate(g)) {
+        segment.add(AppLatLng(sample.latitude!, sample.longitude!));
+      } else {
+        flush();
+      }
+    }
+    flush();
     return polylines;
   }