refactor(nav): single GPS-position accessor + reset COG window after a gap

UITask::currentLocation() becomes the one place that reads the
LocationProvider fix. TrailScreen::ownPos, CompassScreen::gpsValid and
NearbyScreen::refresh now delegate to it instead of each duplicating the
getLocationProvider/isValid dance (and the ENV_INCLUDE_GPS guard).

pushCogFix now restarts the course-over-ground ring when the gap since the
previous fix exceeds 15 s: after losing GPS for a while, a window spanning
the stale old fixes would compute a bogus "teleport" heading. The
last-good heading is kept for display continuity.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

examples/companion_radio/ui-new/CompassScreen.h

@@ -13,14 +13,7 @@
 class CompassScreen : public UIScreen {
   UITask* _task;
 
-  static bool gpsValid() {
-#if ENV_INCLUDE_GPS == 1
-    LocationProvider* loc = sensors.getLocationProvider();
-    return loc && loc->isValid();
-#else
-    return false;
-#endif
-  }
+  bool gpsValid() const { int32_t lat, lon; return _task->currentLocation(lat, lon); }
 
   // Midpoint circle (DisplayDriver has no circle primitive).
   static void drawCircle(DisplayDriver& d, int cx, int cy, int r) {

examples/companion_radio/ui-new/NearbyScreen.h

@@ -111,17 +111,8 @@ class NearbyScreen : public UIScreen {
 
   void refresh() {
     _count = 0;
-    _own_gps = false;
     _own_lat = _own_lon = 0;
-
-#if ENV_INCLUDE_GPS == 1
-    LocationProvider* loc = sensors.getLocationProvider();
-    if (loc && loc->isValid()) {
-      _own_lat = loc->getLatitude();
-      _own_lon = loc->getLongitude();
-      _own_gps = true;
-    }
-#endif
+    _own_gps = _task->currentLocation(_own_lat, _own_lon);
 
     int nc = the_mesh.getNumContacts();
     for (int i = 0; i < nc && _count < MAX_NEARBY; i++) {

examples/companion_radio/ui-new/TrailScreen.h

@@ -357,17 +357,7 @@ private:
   bool selIsStart() const { return hasStart() && _wp_sel == 0; }
   int  wpIndex() const { return _wp_sel - (hasStart() ? 1 : 0); }  // index into WaypointStore
 
-  static bool ownPos(int32_t& lat, int32_t& lon) {
-#if ENV_INCLUDE_GPS == 1
-    LocationProvider* loc = sensors.getLocationProvider();
-    if (loc && loc->isValid()) {
-      lat = (int32_t)loc->getLatitude();
-      lon = (int32_t)loc->getLongitude();
-      return true;
-    }
-#endif
-    return false;
-  }
+  bool ownPos(int32_t& lat, int32_t& lon) const { return _task->currentLocation(lat, lon); }
 
   void handleMarkHere() {
     int32_t lat, lon;

examples/companion_radio/ui-new/UITask.cpp

@@ -1942,11 +1942,17 @@ void UITask::loop() {
 // Insert a GPS fix into the course-over-ground ring, rejecting gross outliers
 // (a jump implying an impossible speed) so one bad fix can't swing the heading.
 void UITask::pushCogFix(int32_t lat, int32_t lon) {
+  static const uint32_t COG_MAX_GAP_MS = 15000;  // GPS gap longer than this → window is stale
   uint32_t now = millis();
   if (_cog_count > 0) {
     const CogFix& prev = _cog[(_cog_head + _cog_count - 1) % COG_RING];
     uint32_t dt = now - prev.ms;
-    if (dt > 0) {
+    if (dt > COG_MAX_GAP_MS) {
+      // GPS was lost for a while: the old fixes are far in the past, so a
+      // window spanning them would imply a bogus "teleport" heading. Restart
+      // the ring from this fix (the last-good _cog_deg is kept for display).
+      _cog_head = 0; _cog_count = 0;
+    } else if (dt > 0) {
       float dist_m = geo::haversineKm(prev.lat, prev.lon, lat, lon) * 1000.0f;
       float speed  = dist_m / (dt / 1000.0f);   // m/s
       if (speed > 50.0f) return;                 // > 180 km/h between fixes → reject
@@ -1978,6 +1984,16 @@ bool UITask::currentCourse(int& deg_out) const {
   return true;
 }
 
+bool UITask::currentLocation(int32_t& lat, int32_t& lon) const {
+  LocationProvider* loc = _sensors ? _sensors->getLocationProvider() : nullptr;
+  if (loc && loc->isValid()) {
+    lat = (int32_t)loc->getLatitude();
+    lon = (int32_t)loc->getLongitude();
+    return true;
+  }
+  return false;
+}
+
 void UITask::saveWaypoints() {
   DataStore* ds = the_mesh.getDataStore();
   if (!ds) return;

examples/companion_radio/ui-new/UITask.h

@@ -152,6 +152,10 @@ public:
   // Current course over ground in degrees (0..359), or false if not enough
   // recent movement to derive a stable heading. Independent of trail logging.
   bool currentCourse(int& deg_out) const;
+  // Current GPS position (1e6-scaled degrees), false when there's no usable
+  // fix. Single source of truth for "where am I", shared by the nav / compass
+  // / map screens so the LocationProvider lookup isn't duplicated per screen.
+  bool currentLocation(int32_t& lat, int32_t& lon) const;
   void playMelody(const char* melody);
   void stopMelody();
   bool isMelodyPlaying();