refactor(ui): rename "Breadcrumb" to "Trail" across the feature

User-facing label change requested for the GPS trail viewer. Carries
through internally for consistency:
- Files: Breadcrumb.h → Trail.h, BreadcrumbScreen.h → TrailScreen.h
- Types: BreadcrumbPoint/Store/Screen → Trail*
- NodePrefs fields: breadcrumb_*_idx → trail_*_idx (same byte layout, no
  sentinel bump needed)
- UITask: _breadcrumb, breadcrumb_screen, gotoBreadcrumbScreen,
  _next_breadcrumb_sample_ms → trail-prefixed equivalents
- Tools menu label "Breadcrumb" → "Trail", screen title "TRAIL"

Status bar indicator stays "G" — semantics ("GPS logging active") match.

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

examples/companion_radio/DataStore.cpp

@@ -305,8 +305,8 @@ void DataStore::loadPrefsInt(const char *filename, NodePrefs& _prefs, double& no
   }
 
   rd(_prefs.favourite_contacts, sizeof(_prefs.favourite_contacts));
-  rd(&_prefs.breadcrumb_interval_idx,  sizeof(_prefs.breadcrumb_interval_idx));
-  rd(&_prefs.breadcrumb_min_delta_idx, sizeof(_prefs.breadcrumb_min_delta_idx));
+  rd(&_prefs.trail_interval_idx,  sizeof(_prefs.trail_interval_idx));
+  rd(&_prefs.trail_min_delta_idx, sizeof(_prefs.trail_min_delta_idx));
 
   // Schema sentinel: bumped on layout changes. Mismatch means an older file
   // (or a different schema); rd() already zero-inits any fields not present,
@@ -405,8 +405,8 @@ void DataStore::savePrefs(const NodePrefs& _prefs, double node_lat, double node_
     file.write((uint8_t *)&_prefs.eink_full_refresh_every, sizeof(_prefs.eink_full_refresh_every));
     file.write((uint8_t *)&_prefs.page_order_set, sizeof(_prefs.page_order_set));
     file.write((uint8_t *)_prefs.favourite_contacts, sizeof(_prefs.favourite_contacts));
-    file.write((uint8_t *)&_prefs.breadcrumb_interval_idx,  sizeof(_prefs.breadcrumb_interval_idx));
-    file.write((uint8_t *)&_prefs.breadcrumb_min_delta_idx, sizeof(_prefs.breadcrumb_min_delta_idx));
+    file.write((uint8_t *)&_prefs.trail_interval_idx,  sizeof(_prefs.trail_interval_idx));
+    file.write((uint8_t *)&_prefs.trail_min_delta_idx, sizeof(_prefs.trail_min_delta_idx));
 
     // Tail sentinel — must be last. See NodePrefs::SCHEMA_SENTINEL.
     uint32_t sentinel = NodePrefs::SCHEMA_SENTINEL;

examples/companion_radio/NodePrefs.h

@@ -99,10 +99,10 @@ struct NodePrefs {  // persisted to file
   static const uint8_t FAVOURITE_PREFIX_LEN = 6;
   uint8_t favourite_contacts[FAVOURITES_COUNT][FAVOURITE_PREFIX_LEN];
 
-  // GPS breadcrumb cadence — indices into BreadcrumbStore::intervalSecs / minDeltaMeters.
-  // Logging on/off is a runtime state (Tools › Breadcrumb), not a persisted preference.
-  uint8_t breadcrumb_interval_idx;   // 0..3: 1min / 30s / 5min / 15min
-  uint8_t breadcrumb_min_delta_idx;  // 0..2: 25m / 5m / 100m
+  // GPS trail cadence — indices into TrailStore::intervalSecs / minDeltaMeters.
+  // Logging on/off is a runtime state (Tools › Trail), not a persisted preference.
+  uint8_t trail_interval_idx;   // 0..3: 1min / 30s / 5min / 15min
+  uint8_t trail_min_delta_idx;  // 0..2: 25m / 5m / 100m
 
   // Tail sentinel written at the end of /new_prefs. Bump the low byte when
   // adding/removing/reordering fields in DataStore::savePrefs/loadPrefsInt so

examples/companion_radio/Trail.h

@@ -4,18 +4,18 @@
 #include <math.h>
 #include <stdint.h>
 
-// RAM-only GPS breadcrumb ring buffer.
+// RAM-only GPS trail ring buffer.
 // Storage cost: 256 × 12 B = 3 KB. The trail survives auto-off (only the
 // display blanks) but is lost on reboot — user explicitly snapshots to a
 // LittleFS slot before powering down to keep it.
 
-struct BreadcrumbPoint {
+struct TrailPoint {
   int32_t  lat_1e6;
   int32_t  lon_1e6;
   uint32_t ts;            // epoch seconds (RTC)
 };
 
-class BreadcrumbStore {
+class TrailStore {
 public:
   static const int CAPACITY = 256;
 
@@ -48,9 +48,9 @@ public:
   bool empty() const { return _count == 0; }
 
   // i = 0 → oldest entry, i = count()-1 → newest.
-  const BreadcrumbPoint& at(int i) const { return _buf[(_head + i) % CAPACITY]; }
-  const BreadcrumbPoint& first() const   { return at(0); }
-  const BreadcrumbPoint& last()  const   { return at(_count - 1); }
+  const TrailPoint& at(int i) const { return _buf[(_head + i) % CAPACITY]; }
+  const TrailPoint& first() const   { return at(0); }
+  const TrailPoint& last()  const   { return at(_count - 1); }
 
   void clear() { _head = 0; _count = 0; }
 
@@ -133,7 +133,7 @@ public:
   }
 
 private:
-  BreadcrumbPoint _buf[CAPACITY];
+  TrailPoint _buf[CAPACITY];
   int  _head   = 0;
   int  _count  = 0;
   bool _active = false;

examples/companion_radio/ui-new/ToolsScreen.h

@@ -44,9 +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; }
+      if (_sel == 4) { _task->gotoTrailScreen(); return true; }
     }
     return false;
   }
 };
-const char* ToolsScreen::ITEMS[5] = { "Ringtone Editor", "Auto-Reply Bot", "Nearby Nodes", "Auto-Advert", "Breadcrumb" };
+const char* ToolsScreen::ITEMS[5] = { "Ringtone Editor", "Auto-Reply Bot", "Nearby Nodes", "Auto-Advert", "Trail" };

examples/companion_radio/ui-new/TrailScreen.h

@@ -1,23 +1,23 @@
 #pragma once
-// GPS breadcrumb viewer. Tools › Breadcrumb.
+// GPS trail viewer. Tools › Trail.
 // Phase 1: Summary view only. Phases 2/3 add Map and List views.
-// Included by UITask.cpp after Breadcrumb store + ToolsScreen.
+// Included by UITask.cpp after Trail store + ToolsScreen.
 
-#include "../Breadcrumb.h"
+#include "../Trail.h"
 
-class BreadcrumbScreen : public UIScreen {
-  UITask*          _task;
-  BreadcrumbStore* _store;
+class TrailScreen : public UIScreen {
+  UITask*     _task;
+  TrailStore* _store;
 
 public:
-  BreadcrumbScreen(UITask* task, BreadcrumbStore* store) : _task(task), _store(store) {}
+  TrailScreen(UITask* task, TrailStore* store) : _task(task), _store(store) {}
 
   void enter() { /* nothing to reset; live trail stays */ }
 
   int render(DisplayDriver& display) override {
     display.setTextSize(1);
     display.setColor(DisplayDriver::LIGHT);
-    display.drawTextCentered(display.width() / 2, 0, "BREADCRUMB");
+    display.drawTextCentered(display.width() / 2, 0, "TRAIL");
     display.fillRect(0, display.headerH() - 1, display.width(), display.sepH());
 
     const int y0   = display.listStart();
@@ -31,7 +31,7 @@ public:
     display.setCursor(2, y0);
     display.print(buf);
 
-    snprintf(buf, sizeof(buf), "Points: %d / %d", _store->count(), BreadcrumbStore::CAPACITY);
+    snprintf(buf, sizeof(buf), "Points: %d / %d", _store->count(), TrailStore::CAPACITY);
     display.setCursor(2, y0 + step);
     display.print(buf);
 

examples/companion_radio/ui-new/UITask.cpp

@@ -116,7 +116,7 @@ static const int QUICK_MSGS_MAX = 10;
 #include "NearbyScreen.h"
 #include "DashboardConfigScreen.h"
 #include "AutoAdvertScreen.h"
-#include "BreadcrumbScreen.h"
+#include "TrailScreen.h"
 #include "ToolsScreen.h"
 
 // ── HomeScreen ────────────────────────────────────────────────────────────────
@@ -403,8 +403,8 @@ class HomeScreen : public UIScreen {
         leftmostX = aX - 1;
       }
 
-      // "G" indicator — GPS breadcrumb logging active. Same blink convention.
-      if (_task->breadcrumb().isActive()) {
+      // "G" indicator — GPS trail logging active. Same blink convention.
+      if (_task->trail().isActive()) {
         int gX = leftmostX - ind;
         bool show_g = Features::BLINK_INDICATORS ? ((millis() % 4000) < 2000) : true;
         if (show_g) {
@@ -1088,7 +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);
+  trail_screen       = new TrailScreen(this, &_trail);
   applyBrightness();
   applyFont();
   applyRotation();
@@ -1125,9 +1125,9 @@ void UITask::gotoDashboardConfig() {
   setCurrScreen(dashboard_config);
 }
 
-void UITask::gotoBreadcrumbScreen() {
-  ((BreadcrumbScreen*)breadcrumb_screen)->enter();
-  setCurrScreen(breadcrumb_screen);
+void UITask::gotoTrailScreen() {
+  ((TrailScreen*)trail_screen)->enter();
+  setCurrScreen(trail_screen);
 }
 
 void UITask::gotoAutoAdvertScreen() {
@@ -1747,19 +1747,19 @@ void UITask::loop() {
     next_batt_chck = millis() + 8000;
   }
 
-  // GPS breadcrumb sampling — runs in the background while the trail is
+  // GPS trail 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;
+  if (_trail.isActive() && _node_prefs != NULL
+      && (int32_t)(millis() - _next_trail_sample_ms) >= 0) {
+    uint16_t interval_s = TrailStore::intervalSecs(_node_prefs->trail_interval_idx);
+    _next_trail_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);
+      uint16_t md = TrailStore::minDeltaMeters(_node_prefs->trail_min_delta_idx);
+      _trail.addPoint((int32_t)loc->getLatitude(),
+                      (int32_t)loc->getLongitude(),
+                      (uint32_t)rtc_clock.getCurrentTime(), md);
     }
   }
 }

examples/companion_radio/ui-new/UITask.h

@@ -22,7 +22,7 @@
 
 #include "../AbstractUITask.h"
 #include "../NodePrefs.h"
-#include "../Breadcrumb.h"
+#include "../Trail.h"
 
 class UITask : public AbstractUITask {
   DisplayDriver* _display;
@@ -74,11 +74,11 @@ class UITask : public AbstractUITask {
   UIScreen* nearby_screen;
   UIScreen* dashboard_config;
   UIScreen* auto_advert_screen;
-  UIScreen* breadcrumb_screen;
+  UIScreen* trail_screen;
   UIScreen* curr;
   CayenneLPP _dash_lpp;
-  BreadcrumbStore _breadcrumb;
-  uint32_t _next_breadcrumb_sample_ms = 0;
+  TrailStore _trail;
+  uint32_t _next_trail_sample_ms = 0;
 
   void userLedHandler();
 
@@ -121,8 +121,8 @@ public:
   void gotoNearbyScreen();
   void gotoDashboardConfig();
   void gotoAutoAdvertScreen();
-  void gotoBreadcrumbScreen();
-  BreadcrumbStore& breadcrumb() { return _breadcrumb; }
+  void gotoTrailScreen();
+  TrailStore& trail() { return _trail; }
   void playMelody(const char* melody);
   void stopMelody();
   bool isMelodyPlaying();