Include and qualify Meshtext in RAK4631 Full Companion

Port Meshtext settings to verified atomic nRF52 storage and use the existing radio RNG and hardware entropy. Keep the ExtraFS boundary, GPS, contacts, channel count and 8 KiB stack unchanged; omit unused library data to fit the image. Require linked codec and Companion transport evidence and build the real RAK Full profile in CI. Add configuration and storage-failure regression coverage.

examples/companion_radio/DataStore.cpp

@@ -371,7 +371,7 @@ static void cleanupAtomicTempFiles(FILESYSTEM* fs) {
       "/_main.id.tmp", "/new_prefs.tmp", "/channels2.tmp",
       "/contacts3.tmp", "/contacts4.mig.tmp", "/adv_blobs.tmp",
       "/.extrafs.mig.tmp", "/extrafs.badpages.tmp",
-      "/extrafs.badpages.bak.tmp"};
+      "/extrafs.badpages.bak.tmp", "/mesh_mt.tmp"};
   for (size_t i = 0; i < sizeof(fixed_temp_paths) / sizeof(fixed_temp_paths[0]); i++) {
     if (fs->exists(fixed_temp_paths[i])) fs->remove(fixed_temp_paths[i]);
   }
@@ -573,6 +573,56 @@ void DataStore::useVolatilePrimaryFS(FILESYSTEM& fs) {
   _contact_load_incomplete = false;
   _prefs_load_incomplete = false;
 }
+
+bool DataStore::loadMeshtextSettings(uint8_t image[40], size_t& size) {
+  size = 0;
+  if (image == nullptr || _fs == nullptr || _primary_storage_unavailable
+      || _volatile_primary_fs) return false;
+  bool present = false;
+  uint32_t stored_size = 0;
+  if (!contactPathPresence(_fs, "/mesh_mt", present, &stored_size)) return false;
+  if (!present) return true;
+  // This backend has never stored the legacy ESP32-only NVS formats. Do not
+  // accept a truncated image, directory or uncommitted .tmp as fresh defaults.
+  if (stored_size != 40) return false;
+  for (uint8_t attempt = 0; attempt < 3; ++attempt) {
+    File file = openRead(_fs, "/mesh_mt");
+    if (!file) continue;
+    uint8_t loaded[40];
+    const bool ok = !file.isDirectory() && file.size() == sizeof(loaded)
+        && file.read(loaded, sizeof(loaded)) == sizeof(loaded);
+    file.close();
+    if (ok) {
+      memcpy(image, loaded, sizeof(loaded));
+      size = sizeof(loaded);
+      return true;
+    }
+  }
+  return false;
+}
+
+bool DataStore::saveMeshtextSettings(const uint8_t image[40]) {
+  if (image == nullptr || _fs == nullptr || _primary_storage_unavailable
+      || _volatile_primary_fs) return false;
+  bool present = false;
+  if (!contactPathPresence(_fs, "/mesh_mt", present)) return false;
+  if (!contactPathPresence(_fs, "/mesh_mt.tmp", present)) return false;
+  if (present && !_fs->remove("/mesh_mt.tmp")) return false;
+  mesh::AtomicFileWriter file(_fs, "/mesh_mt");
+  return file && file.write(image, 40) == 40 && file.commit();
+}
+
+bool DataStore::eraseMeshtextSettings() {
+  if (_fs == nullptr || _primary_storage_unavailable || _volatile_primary_fs) return false;
+  bool present = false;
+  // A staging file must never become a recovery source after explicit erase.
+  for (const char* path : {"/mesh_mt.tmp", "/mesh_mt"}) {
+    if (!contactPathPresence(_fs, path, present)) return false;
+    if (present && !_fs->remove(path)) return false;
+    if (!contactPathPresence(_fs, path, present) || present) return false;
+  }
+  return true;
+}
 #endif
 
 void DataStore::disableSecondaryFS(bool authority_unknown) {