fix(otto): WebSocket direct clients not receiving MCP responses (#1992)

* Enhance Otto Robot camera support by adding configuration for OV3660. Updated config.h to define camera types and GPIO settings, modified config.json to include new camera options, and refactored otto_robot.cc for improved camera detection and initialization logic.

* fix: 移除 OttoEmojiDisplay 构造函数中的 SetTheme 调用以修复 LoadProhibited 崩溃

Made-with: Cursor

* refactor: improve audio service error handling and codec timeout management

- Updated AudioService to prevent input task termination on read timeout, introducing a delay instead.
- Enhanced NoAudioCodec to implement a read timeout for I2S channel reads.
- Adjusted WebSocketControlServer to set a control port for improved socket management.
- Added manufacturer information to the config.json for waveshare ESP32-Touch-LCD-3.5.

* fix(otto): WebSocket direct clients not receiving MCP responses

When a browser connects directly to the WebSocket control server (port
8080) and sends a JSON-RPC request, the MCP response was routed through
Application::SendMcpMessage -> protocol_->SendMcpMessage, which sends it
to the cloud protocol channel. As a result, the direct WebSocket client
never received the response, while the WeChat mini-program could because
it communicates via the cloud.

Fix:
- Add BroadcastMessage() to WebSocketControlServer, using
  httpd_queue_work + httpd_ws_send_frame_async to asynchronously
  send responses back to all connected clients on port 8080
- Add RegisterMcpBroadcastCallback() to Application, allowing an
  additional MCP send callback to be registered; SendMcpMessage()
  now invokes it alongside the cloud protocol
- Register the broadcast callback in OttoRobot after the WebSocket
  server starts successfully

Also add WebSocket direct-connect API documentation to README.md
with complete JSON-RPC 2.0 command examples.

main/boards/otto-robot/websocket_control_server.cc

@@ -190,3 +190,61 @@ void WebSocketControlServer::RemoveClient(httpd_req_t *req) {
 size_t WebSocketControlServer::GetClientCount() const {
     return clients_.size();
 }
+
+struct WsBroadcastJob {
+    httpd_handle_t server;
+    int fd;
+    char* payload;
+    size_t len;
+};
+
+static void ws_broadcast_send_job(void* arg) {
+    WsBroadcastJob* job = static_cast<WsBroadcastJob*>(arg);
+
+    httpd_ws_frame_t ws_pkt = {};
+    ws_pkt.type = HTTPD_WS_TYPE_TEXT;
+    ws_pkt.payload = reinterpret_cast<uint8_t*>(job->payload);
+    ws_pkt.len = job->len;
+    ws_pkt.final = true;
+
+    esp_err_t ret = httpd_ws_send_frame_async(job->server, job->fd, &ws_pkt);
+    if (ret != ESP_OK) {
+        ESP_LOGE("WSControl", "BroadcastMessage: send failed fd=%d err=%d", job->fd, ret);
+    }
+
+    free(job->payload);
+    free(job);
+}
+
+void WebSocketControlServer::BroadcastMessage(const std::string& message) {
+    if (!server_handle_ || clients_.empty()) {
+        return;
+    }
+
+    for (auto& [fd, req] : clients_) {
+        WsBroadcastJob* job = static_cast<WsBroadcastJob*>(malloc(sizeof(WsBroadcastJob)));
+        if (!job) {
+            ESP_LOGE(TAG, "BroadcastMessage: failed to allocate job");
+            continue;
+        }
+
+        job->server = server_handle_;
+        job->fd = fd;
+        job->len = message.length();
+        job->payload = static_cast<char*>(malloc(message.length() + 1));
+        if (!job->payload) {
+            ESP_LOGE(TAG, "BroadcastMessage: failed to allocate payload");
+            free(job);
+            continue;
+        }
+        memcpy(job->payload, message.c_str(), message.length());
+        job->payload[message.length()] = '\0';
+
+        esp_err_t ret = httpd_queue_work(server_handle_, ws_broadcast_send_job, job);
+        if (ret != ESP_OK) {
+            ESP_LOGE(TAG, "BroadcastMessage: httpd_queue_work failed fd=%d err=%d", fd, ret);
+            free(job->payload);
+            free(job);
+        }
+    }
+}