feat(ui): GPS breadcrumb phase 1 — storage, sampling, Summary view

Adds Tools › Breadcrumb. Enter on the screen toggles tracking; while
active, UITask::loop samples GPS at the cadence chosen in settings
(default 1 min) and drops the point into a 256-entry RAM ring guarded
by a min-distance gate (default 25 m). A "G" indicator joins "A" in
the status bar with the same blink convention.

New storage:
- examples/companion_radio/Breadcrumb.h — BreadcrumbStore class
- 256 × 12 B = 3 KB RAM (survives auto-off, lost on reboot — explicit
  flash-slot save comes in phase 4)
- Haversine min-delta gate, total distance, elapsed seconds, current
  km/h, bounding-box helper

New screen:
- examples/companion_radio/ui-new/BreadcrumbScreen.h — Summary view
  with Status, Points, Dist (m or km), Time (h:mm), Speed; Enter
  toggles tracking, Esc returns to Tools

Schema bump 0xC0DE0002 → 0xC0DE0003 for two new NodePrefs bytes:
breadcrumb_interval_idx (1min default) and breadcrumb_min_delta_idx
(25m default). Older saves leave both at zero, which matches the new
defaults. DataStore::loadPrefsInt/savePrefs read/write the pair.

Logging on/off is a runtime flag inside BreadcrumbStore — not a
preference — so reboot returns to the off state cleanly; the user
will be able to persist a snapshot to a slot in phase 4.

Phase 2 (map view), 3 (point list), 4 (slot save/load, GPX export over
USB), and 5 (settings UI) follow incrementally.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/companion_radio/ui-new/ToolsScreen.h

@@ -6,7 +6,7 @@ class ToolsScreen : public UIScreen {
   UITask* _task;
   int _sel;
 
-  static const int ITEM_COUNT = 4;
+  static const int ITEM_COUNT = 5;
   static const char* ITEMS[ITEM_COUNT];
 
 public:
@@ -44,8 +44,9 @@ public:
       if (_sel == 1) { _task->gotoBotScreen();        return true; }
       if (_sel == 2) { _task->gotoNearbyScreen();     return true; }
       if (_sel == 3) { _task->gotoAutoAdvertScreen(); return true; }
+      if (_sel == 4) { _task->gotoBreadcrumbScreen(); return true; }
     }
     return false;
   }
 };
-const char* ToolsScreen::ITEMS[4] = { "Ringtone Editor", "Auto-Reply Bot", "Nearby Nodes", "Auto-Advert" };
+const char* ToolsScreen::ITEMS[5] = { "Ringtone Editor", "Auto-Reply Bot", "Nearby Nodes", "Auto-Advert", "Breadcrumb" };