refactor(companion): unify every reboot/power-off through UITask::shutdown()

Settings > Reboot, the phone app's CMD_REBOOT, and the serial CLI's
"reboot" command each hand-rolled their own flush-then-board.reboot()
sequence, so each could drift independently (Settings > Reboot and the
CLI command were both missing the contacts flush added in the previous
commit). Add a pure-virtual AbstractUITask::shutdown(bool restart) --
every UI variant (ui-new/ui-tiny/ui-orig) already implements a method
with this exact signature -- and route all three call sites through it
instead. CMD_FACTORY_RESET intentionally keeps calling board.reboot()
directly: flushing stale in-RAM prefs back out would defeat the format
it just did.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

examples/companion_radio/AbstractUITask.h

@@ -148,5 +148,12 @@ public:
   // added later at the same slot would silently inherit the old one's bot/
   // share target or notification melody. Default no-op.
   virtual void onChannelRemoved(uint8_t channel_idx) {}
+  // Single choke point for every controlled power-down (low-battery auto-off,
+  // long-press power-off, and now every board.reboot() caller too): flush
+  // prefs/RTC/contacts/trail before the board actually goes down or restarts,
+  // so no exit path can silently skip a pending write. restart=true reboots,
+  // false powers off. Every UI variant (ui-new/ui-tiny/ui-orig) implements
+  // this the same way -- see each's UITask::shutdown().
+  virtual void shutdown(bool restart = false) = 0;
   virtual void loop() = 0;
 };

examples/companion_radio/MyMesh.cpp

@@ -2380,11 +2380,13 @@ void MyMesh::handleCmdFrame(size_t len) {
       writeOKFrame();
     }
   } else if (cmd_frame[0] == CMD_REBOOT && memcmp(&cmd_frame[1], "reboot", 6) == 0) {
-    if (dirty_contacts_expiry) { // is there are pending dirty contacts write needed?
-      saveContacts();
-    }
-    savePrefs();  // flush any on-device setting change not yet persisted -- see UITask::shutdown()'s comment
+    if (_ui) {
+      _ui->shutdown(true);
+    } else {
+      flushDirtyContacts();
+      savePrefs();
       board.reboot();
+    }
   } else if (cmd_frame[0] == CMD_GET_BATT_AND_STORAGE) {
     uint8_t reply[11];
     int i = 0;
@@ -3192,8 +3194,13 @@ void MyMesh::checkCLIRescueCmd() {
       }
 
     } else if (strcmp(cli_command, "reboot") == 0) {
+      if (_ui) {
+        _ui->shutdown(true);
+      } else {
+        flushDirtyContacts();
         savePrefs();  // flush any on-device setting change not yet persisted -- see UITask::shutdown()'s comment
         board.reboot();  // doesn't return
+      }
     } else {
       Serial.println("  Error: unknown command");
     }

examples/companion_radio/ui-new/SettingsScreen.h

@@ -1018,9 +1018,8 @@ public:
       return true;
     }
     if (_selected == REBOOT && enter) {
-      _task->savePrefsIfDirty(_dirty);   // don't lose pending edits across the restart
       _task->showAlert("Rebooting...", 800);
-      board.reboot();
+      _task->shutdown(true);   // flushes prefs/RTC/contacts/trail, then reboots -- single choke point
       return true;
     }
     if (_selected == KEYBOARD_TYPE && p && (left || right || enter)) {