refactor(errors): normalize user-facing error messages

src/core/net/chat-websocket.ts

@@ -9,6 +9,7 @@
  *   - onError(errorMessage)
  */
 import { getApiConfig } from "@/core/net/config/api_config";
+import { ExceptionHandler } from "@/core/errors";
 import { AppEnvUtil, Logger } from "@/utils";
 
 const log = new Logger("ChatWebSocket");
@@ -89,7 +90,9 @@ export class ChatWebSocket {
       };
     } catch (e) {
       logWebSocketError("✕ WS CONNECT FAILED", e);
-      this.onError?.(e instanceof Error ? e.message : String(e));
+      this.onError?.(
+        ExceptionHandler.message(e, "WebSocket connection failed."),
+      );
     }
   }