feat(nav): standalone Compass in Tools

Tools › Compass shows the device's course over ground (from the GPS COG
ring — no magnetometer) as a rotating arrow in a ring with a north tick,
plus a large degrees + cardinal readout. "No GPS fix" without a fix;
"move to set heading" when stationary (course undefined). Reuses
UITask::currentCourse, so it works without recording a trail.

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

examples/companion_radio/ui-new/UITask.h

@@ -76,6 +76,7 @@ class UITask : public AbstractUITask {
   UIScreen* dashboard_config;
   UIScreen* auto_advert_screen;
   UIScreen* trail_screen;
+  UIScreen* compass_screen;
   UIScreen* curr;
   CayenneLPP _dash_lpp;
   TrailStore _trail;
@@ -144,6 +145,7 @@ public:
   void gotoDashboardConfig();
   void gotoAutoAdvertScreen();
   void gotoTrailScreen();
+  void gotoCompassScreen();
   TrailStore& trail() { return _trail; }
   WaypointStore& waypoints() { return _waypoints; }
   void saveWaypoints();   // persist the table to /waypoints