fix: 修复 AI 检索 Evidence 覆盖与加载更多问题

修复问一问微信查询遗漏群聊的问题
区分会话覆盖与发送者覆盖策略
新增问一问微信加载更多功能

tests/unit/ai-search-time-range.test.ts

@@ -74,7 +74,7 @@ describe('AI search natural-language time ranges', () => {
 
   it('classifies global topics and bare conversation names without turning names into FTS terms', () => {
     expect(buildLocalAiSearchPlan('最近谁聊过 MCP？')).toMatchObject({
-      intent: 'global_topic_search',
+      intent: 'global_sender_topic_search',
       topicQuery: 'MCP',
       keywords: ['MCP']
     })
@@ -95,6 +95,26 @@ describe('AI search natural-language time ranges', () => {
     })
   })
 
+  it('classifies group conversation questions separately from sender questions', () => {
+    for (const question of [
+      '哪个群聊过 WechatExplorer',
+      '哪些群聊过 WechatExplorer',
+      '哪些群讨论过 WechatExplorer',
+      '哪个群说过 WechatExplorer'
+    ]) {
+      expect(buildLocalAiSearchPlan(question)).toMatchObject({
+        intent: 'global_group_topic_search',
+        topicQuery: 'WechatExplorer',
+        keywords: ['WechatExplorer']
+      })
+    }
+    expect(buildLocalAiSearchPlan('谁聊过 WechatExplorer')).toMatchObject({
+      intent: 'global_sender_topic_search',
+      topicQuery: 'WechatExplorer',
+      keywords: ['WechatExplorer']
+    })
+  })
+
   it('matches an explicitly mentioned nickname when the user omits punctuation', () => {
     expect(includesExplicitAiSearchAlias('我和中田健身弘毅最近聊了什么？', '中田健身-弘毅')).toBe(
       true