refactor: 更新任务表单组件以使用错误消息替代帮助文本，简化任务上下文中的任务查找逻辑

src/components/TaskForm.tsx

@@ -1,4 +1,4 @@
-import React, { useState, useEffect } from 'react';
+import React, { useEffect } from 'react';
 import { StyleSheet, ScrollView, Text, View } from 'react-native';
 import { Input } from '@rneui/themed';
 import { Task, RobotAction, InputParam } from '../types/task';
@@ -48,7 +48,7 @@ const TaskForm: React.FC<TaskFormProps> = ({ task, onTaskChange }) => {
             value={value as string}
             onChangeText={text => handleParamChange(param.name, text)}
             placeholder={param.remark}
-            helperText={param.remark}
+            errorMessage={param.remark}
             inputContainerStyle={styles.inputContainer}
           />
         );
@@ -60,7 +60,7 @@ const TaskForm: React.FC<TaskFormProps> = ({ task, onTaskChange }) => {
             value={value as string}
             onChangeText={text => handleParamChange(param.name, text)}
             placeholder={param.remark}
-            helperText={param.remark}
+            errorMessage={param.remark}
             inputContainerStyle={styles.inputContainer}
           />
         );

src/context/TasksContext.tsx

@@ -14,7 +14,6 @@ import {
 } from '../types/config';
 import {
   getConfig,
-  getSettings,
   executeTask,
   clearCachedConfig,
 } from '../services/configService';
@@ -141,7 +140,7 @@ export const TasksProvider: React.FC<{ children: ReactNode }> = ({
       await clearCachedConfig();
       const config = await getConfig();
       if (config) {
-        applyConfig(config, false); // Don't load tasks from config
+        applyConfig(config); // Don't load tasks from config
         setIsConfigLoaded(true);
         if (config.serverUrl && config.apiEndpoints) {
           await fetchTasks(config.serverUrl, config.apiEndpoints.getTasks);
@@ -157,7 +156,7 @@ export const TasksProvider: React.FC<{ children: ReactNode }> = ({
   };
 
   const getTaskById = (id: string) => {
-    const task = tasks.find(task => task.id === id);
+    const task = tasks.find(t => t.id === id);
     if (task && !task.detail) {
       fetchTaskDetail(id);
     }

src/services/configService.ts

@@ -6,7 +6,8 @@ const CONFIG_CACHE_KEY = 'cached_config';
 
 // 默认设置
 const DEFAULT_SETTINGS: AppSettings = {
-  configFileName: 'config',
+  configFileName: 'config.json',
+  serverUrl: '',
 };
 
 // 获取设置