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/UITask.cpp

@@ -116,6 +116,7 @@ static const int QUICK_MSGS_MAX = 10;
 #include "NearbyScreen.h"
 #include "DashboardConfigScreen.h"
 #include "AutoAdvertScreen.h"
+#include "BreadcrumbScreen.h"
 #include "ToolsScreen.h"
 
 // ── HomeScreen ────────────────────────────────────────────────────────────────
@@ -401,6 +402,21 @@ class HomeScreen : public UIScreen {
         }
         leftmostX = aX - 1;
       }
+
+      // "G" indicator — GPS breadcrumb logging active. Same blink convention.
+      if (_task->breadcrumb().isActive()) {
+        int gX = leftmostX - ind;
+        bool show_g = Features::BLINK_INDICATORS ? ((millis() % 4000) < 2000) : true;
+        if (show_g) {
+          display.setColor(DisplayDriver::LIGHT);
+          display.fillRect(gX, 0, ind, ind_h);
+          display.setColor(DisplayDriver::DARK);
+          display.setCursor(gX + 1, 0);
+          display.print("G");
+          display.setColor(DisplayDriver::LIGHT);
+        }
+        leftmostX = gX - 1;
+      }
     }
     return leftmostX;
   }
@@ -1072,6 +1088,7 @@ void UITask::begin(DisplayDriver* display, SensorManager* sensors, NodePrefs* no
   nearby_screen = new NearbyScreen(this);
   dashboard_config = new DashboardConfigScreen(this, node_prefs);
   auto_advert_screen = new AutoAdvertScreen(this, node_prefs);
+  breadcrumb_screen  = new BreadcrumbScreen(this, &_breadcrumb);
   applyBrightness();
   applyFont();
   applyRotation();
@@ -1108,6 +1125,11 @@ void UITask::gotoDashboardConfig() {
   setCurrScreen(dashboard_config);
 }
 
+void UITask::gotoBreadcrumbScreen() {
+  ((BreadcrumbScreen*)breadcrumb_screen)->enter();
+  setCurrScreen(breadcrumb_screen);
+}
+
 void UITask::gotoAutoAdvertScreen() {
   ((AutoAdvertScreen*)auto_advert_screen)->enter();
   setCurrScreen(auto_advert_screen);
@@ -1724,6 +1746,22 @@ void UITask::loop() {
     }
     next_batt_chck = millis() + 8000;
   }
+
+  // GPS breadcrumb sampling — runs in the background while the trail is
+  // active, independent of which screen is shown. Skips silently if no GPS
+  // fix; min-delta gate inside addPoint() avoids near-stationary spam.
+  if (_breadcrumb.isActive() && _node_prefs != NULL
+      && (int32_t)(millis() - _next_breadcrumb_sample_ms) >= 0) {
+    uint16_t interval_s = BreadcrumbStore::intervalSecs(_node_prefs->breadcrumb_interval_idx);
+    _next_breadcrumb_sample_ms = millis() + (uint32_t)interval_s * 1000UL;
+    LocationProvider* loc = _sensors ? _sensors->getLocationProvider() : nullptr;
+    if (loc && loc->isValid()) {
+      uint16_t md = BreadcrumbStore::minDeltaMeters(_node_prefs->breadcrumb_min_delta_idx);
+      _breadcrumb.addPoint((int32_t)loc->getLatitude(),
+                            (int32_t)loc->getLongitude(),
+                            (uint32_t)rtc_clock.getCurrentTime(), md);
+    }
+  }
 }
 
 char UITask::checkDisplayOn(char c) {