feat: 增强输入框状态管理，添加禁用状态和恢复输入状态的逻辑

src/utils/messageHandler.ts

@@ -96,6 +96,12 @@ export async function handleUserMessage(
         text: "后端服务不可用",
         type: "error",
       });
+      // 恢复输入状态
+      panel.webview.postMessage({
+        command: "updateSegments",
+        segments: [],
+        isComplete: true,
+      });
       throw error;
     }
   }
@@ -255,6 +261,12 @@ async function handleUserMessageWithBackend(
             command: "receiveMessage",
             text: `❌ 错误: ${message}`,
           });
+          // 恢复输入状态
+          panel.webview.postMessage({
+            command: "updateSegments",
+            segments: [],
+            isComplete: true,
+          });
           reject(new Error(message));
         },