fix(chat): fix ChatBloc event callback and test reliability

- Fix onEvent callback initialization in ChatBloc constructor
- Add MockAgUiService to isolate test from mock API behavior
- Remove unnecessary non-null assertions in tests

apps/lib/features/chat/ui/widgets/ui_schema_renderer.dart

@@ -2,16 +2,19 @@ import 'package:flutter/material.dart';
 import 'package:social_app/core/theme/design_tokens.dart';
 import '../../data/models/tool_result.dart';
 
+/// 卡片类型常量
+const _calendarCardType = 'calendar_card.v1';
+const _errorCardType = 'error_card.v1';
+const _aiGeneratedSource = 'ai_generated';
+const _primaryActionType = 'primary';
+
 class UiSchemaRenderer {
   static Widget render(UiCard card) {
-    switch (card.cardType) {
-      case 'calendar_card.v1':
-        return _renderCalendarCard(card);
-      case 'error_card.v1':
-        return _renderErrorCard(card);
-      default:
-        return _renderUnknownCard(card);
-    }
+    return switch (card.cardType) {
+      _calendarCardType => _renderCalendarCard(card),
+      _errorCardType => _renderErrorCard(card),
+      _ => _renderUnknownCard(card),
+    };
   }
 
   static Widget _renderCalendarCard(UiCard card) {
@@ -19,6 +22,7 @@ class UiSchemaRenderer {
     final color = data.color != null
         ? Color(int.parse(data.color!.replaceFirst('#', '0xFF')))
         : AppColors.blue500;
+    final isAiGenerated = data.sourceType == _aiGeneratedSource;
 
     return Container(
       decoration: BoxDecoration(
@@ -44,23 +48,10 @@ class UiSchemaRenderer {
             child: Column(
               crossAxisAlignment: CrossAxisAlignment.start,
               children: [
-                if (data.sourceType == 'ai_generated')
-                  Container(
-                    padding: EdgeInsets.symmetric(
-                      horizontal: AppSpacing.sm,
-                      vertical: AppSpacing.xs,
-                    ),
-                    decoration: BoxDecoration(
-                      color: AppColors.messageTagBg,
-                      borderRadius: BorderRadius.circular(AppRadius.sm),
-                    ),
-                    child: Text(
-                      'AI生成',
-                      style: TextStyle(fontSize: 10, color: AppColors.blue600),
-                    ),
-                  ),
-                if (data.sourceType == 'ai_generated')
+                if (isAiGenerated) ...[
+                  _buildAiTag(),
                   SizedBox(height: AppSpacing.sm),
+                ],
                 Text(
                   _formatTime(data.startAt, data.endAt),
                   style: TextStyle(fontSize: 12, color: AppColors.slate500),
@@ -83,32 +74,11 @@ class UiSchemaRenderer {
                 ],
                 if (data.location != null) ...[
                   SizedBox(height: AppSpacing.sm),
-                  Row(
-                    children: [
-                      Icon(
-                        Icons.location_on_outlined,
-                        size: 16,
-                        color: AppColors.slate500,
-                      ),
-                      SizedBox(width: AppSpacing.xs),
-                      Text(
-                        data.location!,
-                        style: TextStyle(
-                          fontSize: 12,
-                          color: AppColors.slate500,
-                        ),
-                      ),
-                    ],
-                  ),
+                  _buildLocation(data.location!),
                 ],
                 if (card.actions != null && card.actions!.isNotEmpty) ...[
                   SizedBox(height: AppSpacing.md),
-                  Wrap(
-                    spacing: AppSpacing.sm,
-                    children: card.actions!
-                        .map((action) => _buildActionButton(action))
-                        .toList(),
-                  ),
+                  _buildActions(card.actions!),
                 ],
               ],
             ),
@@ -118,8 +88,45 @@ class UiSchemaRenderer {
     );
   }
 
+  static Widget _buildAiTag() {
+    return Container(
+      padding: EdgeInsets.symmetric(
+        horizontal: AppSpacing.sm,
+        vertical: AppSpacing.xs,
+      ),
+      decoration: BoxDecoration(
+        color: AppColors.messageTagBg,
+        borderRadius: BorderRadius.circular(AppRadius.sm),
+      ),
+      child: Text(
+        'AI生成',
+        style: TextStyle(fontSize: 10, color: AppColors.blue600),
+      ),
+    );
+  }
+
+  static Widget _buildLocation(String location) {
+    return Row(
+      children: [
+        Icon(Icons.location_on_outlined, size: 16, color: AppColors.slate500),
+        SizedBox(width: AppSpacing.xs),
+        Text(
+          location,
+          style: TextStyle(fontSize: 12, color: AppColors.slate500),
+        ),
+      ],
+    );
+  }
+
+  static Widget _buildActions(List<CardAction> actions) {
+    return Wrap(
+      spacing: AppSpacing.sm,
+      children: actions.map((action) => _buildActionButton(action)).toList(),
+    );
+  }
+
   static Widget _buildActionButton(CardAction action) {
-    final isPrimary = action.type == 'primary';
+    final isPrimary = action.type == _primaryActionType;
     return GestureDetector(
       onTap: () => _handleAction(action),
       child: Container(