fix: review fixes for the OTA slot

- The field is hasOtaSlot, like hasEthernet and the other "has" bools.
- The web UI shows the device's reason for any failed upload, not only
  for /restore, so it shows "no OTA slot" from a page that missed the
  header. The update routes' 500 replies give Update.errorString()
  instead of an empty reason.
- Native: the writer leaves hasOtaSlot out when true and writes "os":0.
- e2e: header() next to uptime(); the test skips on firmware without
  the field instead of failing, and matches the reason loosely. The
  README says what the test sends.
- PROTOCOL.md and the comments name only the builds that exist.

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

src/ConfigSettings.cpp

@@ -145,7 +145,7 @@ bool ConfigSettings::begin() {
       break;
   }
   ESP_LOGD(TAG, "Chip Model ESP32-%s", this->chipModel);
-  this->otaSlot = esp_ota_get_next_update_partition(nullptr) != nullptr;
+  this->hasOtaSlot = esp_ota_get_next_update_partition(nullptr) != nullptr;
   this->fwVersion.parse(FW_VERSION);
   uint64_t mac = ESP.getEfuseMac();
   for(int i=0; i<17; i=i+8) {

src/ConfigSettings.h

@@ -164,8 +164,8 @@ class ConfigSettings: BaseSettings {
     char hostname[32] = "ESPSomfyRTS";
     char chipModel[10] = "ESP32";
     // Whether the partition table has a second app slot for /updateFirmware
-    // to write.  Builds with one 3 MB slot (C5, C6, debug) are flashed over USB.
-    bool otaSlot = true;
+    // to write.  Builds with one 3 MB slot (C6, debug) are flashed over USB.
+    bool hasOtaSlot = true;
     conn_types_t connType = conn_types_t::unset;
     appver_t fwVersion;
     appver_t appVersion;

src/ProtoSchema.h

@@ -169,7 +169,7 @@
   FIELD(hostname, "hn", 's', 0) \
   FIELD(model, "md", 's', 0) \
   FIELD(chipModel, "cp", 's', 0) \
-  FIELD(otaSlot, "os", 'b', 1) \
+  FIELD(hasOtaSlot, "os", 'b', 1) \
   FIELD(connType, "ct", 's', 0) \
   /* memory, wifi and ethernet */ \
   FIELD(freeHeap, "fr", 'i', 0) \

src/entryPoints/HttpRoutes.cpp

@@ -165,19 +165,20 @@ void registerHttpRoutes(AsyncWebServer &server) {
   server.on(AsyncURIMatcher::exact("/updateFirmware"), HTTP_POST,
     [](AsyncWebServerRequest *request) {
       // Nothing was written or stopped, so there is nothing to reboot for.
-      if(!settings.otaSlot) {
+      if(!settings.hasOtaSlot) {
         request->send(400, _encoding_json, F("{\"status\":\"ERROR\",\"desc\":\"This device has no OTA slot, so its firmware is flashed over USB.\"}"));
         return;
       }
+      // errorString() is one of the updater's fixed messages, none with a quote.
       if(Update.hasError())
-        request->send(500, _encoding_json, "{\"status\":\"ERROR\",\"desc\":\"Error updating firmware: \"}");
+        request->send(500, _encoding_json, String("{\"status\":\"ERROR\",\"desc\":\"Error updating firmware: ") + Update.errorString() + "\"}");
       else
         request->send(200, _encoding_json, "{\"status\":\"SUCCESS\",\"desc\":\"Successfully updated firmware\"}");
       rebootDelay.reboot = true;
       rebootDelay.rebootTime = millis() + 500;
     },
     [](AsyncWebServerRequest *request, String filename, size_t index, uint8_t *data, size_t len, bool final) {
-      if(!uploadAllowed(request, index) || !settings.otaSlot) return;
+      if(!uploadAllowed(request, index) || !settings.hasOtaSlot) return;
       if(index == 0) {
         webServer.uploadSuccess = false;
         ESP_LOGI(TAG, "Update: %s", filename.c_str());
@@ -212,7 +213,7 @@ void registerHttpRoutes(AsyncWebServer &server) {
   server.on(AsyncURIMatcher::exact("/updateApplication"), HTTP_POST,
     [](AsyncWebServerRequest *request) {
       if(Update.hasError())
-        request->send(500, _encoding_json, "{\"status\":\"ERROR\",\"desc\":\"Error updating application: \"}");
+        request->send(500, _encoding_json, String("{\"status\":\"ERROR\",\"desc\":\"Error updating application: ") + Update.errorString() + "\"}");
       else
         request->send(200, _encoding_json, "{\"status\":\"SUCCESS\",\"desc\":\"Successfully updated application\"}");
       rebootDelay.reboot = true;

src/outputs/ProtoSocket.cpp

@@ -77,7 +77,7 @@ static void writeHeader(ProtoWriter &w) {
   w.add(proto_field_t::hostname, settings.hostname);
   w.add(proto_field_t::model, "ESPSomfyRTS");
   w.add(proto_field_t::chipModel, settings.chipModel);
-  w.add(proto_field_t::otaSlot, settings.otaSlot);
+  w.add(proto_field_t::hasOtaSlot, settings.hasOtaSlot);
   w.add(proto_field_t::fw, settings.fwVersion.name);
   w.add(proto_field_t::connType, net.connTypeName());
 }