排查转发bug同类问题：修复查找聊天记录崩溃 + 复制功能复制出"undefined"

审查了所有"读取消息content做数据处理"的地方，找到两处和转发bug同一根因
(手机端扁平非Drafty内容格式)的真实问题：

1. 查找聊天记录(HistorySearchModal)的搜索结果渲染，对手机端发送的图片/文件/
   语音/视频/名片消息命中关键词时会让整个应用崩溃——Drafty.toPlainText在这
   类扁平内容上返回undefined，highlightMatches对undefined调用.toLowerCase()
   直接抛异常，而这个应用完全没有错误边界(ErrorBoundary)兜底，等于白屏。
   已用真实搜索接口返回确认snapshot里其实带着head字段(此前SearchHit类型
   没建模)，据此在渲染前识别这几种扁平内容并显示[图片]/[文件]/[语音]/[名片]
   这样的占位文案，不再无脑喂给renderDrafty；顺手给highlightMatches补了防御
   性判空，避免类似疏漏再次崩溃整个应用。

2. 消息右键菜单"复制"功能，对手机端发送的扁平文本消息(如群公告自动发布的
   那条)和图片/文件/语音/视频消息，复制到剪贴板的是字面字符串"undefined"。
   文本类修成正确提取真实文本；附件类直接从"复制"这个操作里去掉(参考名片/
   通话记录消息已有的排除逻辑)，复制一段JSON式的附件数据本来就没有意义。

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/features/messages/HistorySearchModal.tsx

@@ -8,6 +8,7 @@ import { getTopicMedia, searchTopicMessages, type MediaFetchType, type MediaItem
 import { checkUrlSafety } from '@/lib/api/security';
 import { avatarBgClass, avatarLetter } from '@/lib/avatar';
 import { useAuthedBlobUrl, useDebouncedValue, useEscapeKey } from '@/lib/hooks';
+import { contactCardContentOf, mobileAttachmentContentOf } from '@/lib/messages/dispatch';
 import { renderDrafty } from '@/lib/messages/drafty';
 import { groupSenderLabel } from '@/lib/messages/sender-name';
 import { formatEventTimestamp } from '@/lib/messages/time';
@@ -68,10 +69,34 @@ function MediaThumb({ item, isVideo }: { item: MediaItem; isVideo: boolean }) {
  *  through rather than picking fields back out of it by hand. The previous version's manual
  *  `{txt:content.txt||' ', ...}` reconstruction silently produced a single blank space for the bare-
  *  string case (`content.txt` on a string primitive is `undefined`), which is exactly what a live
- *  search against a real plain-text message showed before this fix. */
+ *  search against a real plain-text message showed before this fix.
+ *
+ *  Real, DB/API-confirmed bug fixed here (2026-09-24): a mobile-sent message's `snapshot.content` is
+ *  a FLAT, non-Drafty object (`{text:...}` for text, `{file_id,...}` for image/file/voice/video,
+ *  `{user_id,...}` for a contact card), tagged only by `snapshot.head['x-im-type']` -- confirmed live
+ *  via a real search hit's raw network response (`snapshot.head` IS present despite not previously
+ *  being modeled on `SearchHit`, same as favorites.ts's own snapshot). Handing that straight to
+ *  `renderDrafty` used to crash the WHOLE APP the moment a keyword matched one (`Drafty.toPlainText`
+ *  returns `undefined` for a shape with no `.txt`, and `highlightMatches` then called `.toLowerCase()`
+ *  on it -- this app has no error boundary anywhere to contain that). Same root cause, and same fix
+ *  approach, as `forwardMessage()`'s own `flatForwardPayload` (lib/tinode/send.ts). */
 function SnapshotContent({ item, highlightQuery }: { item: SearchHit; highlightQuery?: string }) {
   const content = item.snapshot?.content;
   if (!content) return <span className="text-text-tertiary-4">（内容不可用）</span>;
+  const asMessage = { content, head: item.snapshot?.head } as Parameters<typeof mobileAttachmentContentOf>[0];
+  const mobileAttachment = mobileAttachmentContentOf(asMessage);
+  if (mobileAttachment) {
+    const label =
+      mobileAttachment.kind === 'image'
+        ? '[图片]'
+        : mobileAttachment.kind === 'video'
+          ? '[视频]'
+          : mobileAttachment.kind === 'voice'
+            ? '[语音]'
+            : `[文件] ${mobileAttachment.name || ''}`;
+    return <span className="text-text-body">{label}</span>;
+  }
+  if (contactCardContentOf(asMessage)) return <span className="text-text-body">[名片]</span>;
   return <div className="text-sm text-text-body">{renderDrafty(content, highlightQuery)}</div>;
 }