refactor(ui): remove dead code and fix stale comments after the review

- ui-core: Diagnostics::systemLines, NearbyModel::typeShort,
  rptctl::currentPresetName, RoomSessions::pendingKey, settings::isSwitch,
  UiCore::reconcileDMUnread.
- ui-new: the retired Recent page, fmtAlt, the battMvToPercent wrapper,
  setFavouriteChannelSlot, AccordionList onHeader/visibleCount, drawBoxedIcon
  and seven unused icons; info::row folded into info::valueRow.
- ui-lvgl: onOpenNav, TileDownloader::withTrails; the trail header size is
  one constant (TRAIL_HDR) for live and saved trails.
- Home quick panels save prefs only when a value changed.
- Comments brought in line with the code (status bar reserve, settings rows,
  page order, SH1106 frame skip, UiCore header).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/companion_radio/ui-lvgl/NavMap.h

@@ -1131,7 +1131,7 @@ bool UITask::saveTrailToCard(char* name_out, size_t n) {
 // ring (the oldest points dropping off) is rewritten, at most every 10 min.
 namespace navmap {
 static const char* const LIVE_TRAIL = "/sdcard/trails/.live.trl";
-static const long LIVE_HDR = 12;   // magic, version, reserved, count (uint16), time (uint32)
+static const long TRAIL_HDR = 12;   // a trail file's header (TrailStore::writeTo): magic, version, flags, count (uint16), time (uint32)
 static uint32_t s_j_gen = 0xFFFFFFFF, s_j_seq = 0, s_j_next = 0, s_j_full_at = 0;
 static int s_j_n = 0;
 static uint8_t s_j_rec = 0;   // the "recording" byte last written
@@ -1202,7 +1202,7 @@ void UITask::savedTrailsPopup() {
     navmap::trailTitle(navmap::s_st_names[i], title, sizeof(title));
     snprintf(path, sizeof(path), "%s/%s", navmap::TRAILS_DIR, navmap::s_st_names[i]);
     struct stat st;
-    long pts = stat(path, &st) == 0 ? ((long)st.st_size - 12) / (long)sizeof(TrailPoint) : 0;
+    long pts = stat(path, &st) == 0 ? ((long)st.st_size - navmap::TRAIL_HDR) / (long)sizeof(TrailPoint) : 0;
     snprintf(sub, sizeof(sub), "%ld points", pts > 0 ? pts : 0);
     listRow(list, title, sub, onSavedTrail, (void*)(intptr_t)i);
   }

examples/companion_radio/ui-lvgl/UITask.cpp

@@ -2786,7 +2786,6 @@ static void onOpenSettings(lv_event_t* e) { (void)e; s_ui->showSettings(); }
 
 static void onOpenNearby(lv_event_t* e) { (void)e; s_ui->showNearby(); }
 static void onOpenNodesMap(lv_event_t* e) { (void)e; s_ui->openMap(false); }
-static void onOpenNav(lv_event_t* e) { (void)e; s_ui->openMap(true); }
 static void onOpenClock(lv_event_t* e);   // ClockScreen.h
 static void onOpenBot(lv_event_t* e);     // BotScreen.h
 static void onOpenCompass(lv_event_t* e);   // CompassScreen.h

examples/companion_radio/ui-lvgl/map/TileDownloader.h

@@ -95,7 +95,6 @@ public:
 
   State state() const       { return _state; }
   const TileArea& area() const { return _area; }   // of the current / last job
-  bool withTrails() const   { return _trails; }
   bool  active() const      { return _state == CONNECTING || _state == RUNNING; }
   uint32_t total() const    { return _total; }
   uint32_t processed() const { return _done + _skipped + _failed; }