🐛 fix(im)：codex 评审修复发送中状态边角

- recomputeConversationLast 空 messages 时一并清 lastSendTime，
  避免刷新后被 drop 的媒体占位让空会话仍按旧时间排在列表前面
- 视频占位 coverUrl 不再赋 blob URL：<video poster> 期待图片资源，
  传 video blob 在部分浏览器会退化成黑底，cover 等 probe 出真实 URL 后由 commit 阶段一起 patch
- useMediaUploader 暴露 requireMediaHandler typed accessor，
  消除 video 链路 mediaTypeHandlers[VIDEO]! 非空断言
- MessageItem 把外层 loading 的 (!isUploading || isVoice) 抽成 showSendingLoading computed

src/views/im/home/composables/useMediaUploader.ts

@@ -35,7 +35,7 @@ export interface MediaTypeContext {
   videoCoverUrl?: string
 }
 
-interface MediaTypeHandler {
+export interface MediaTypeHandler {
   /** 中文名，仅日志用（替代之前散落 9 处的 kind 字符串） */
   kind: string
   /** 由 file + url + context 生成 payload；占位时 url 是 blob URL，commit 时是真实 url */
@@ -201,6 +201,20 @@ export const useMediaUploader = () => {
   /** 取媒体类型中文名（仅日志用）；未注册 type 退化为通用「媒体」 */
   const getMediaKind = (type: number): string => mediaTypeHandlers[type]?.kind ?? '媒体'
 
+  /**
+   * 按 type 取 handler，缺则抛错（程序错误集中在这一处）
+   *
+   * 调用方拿到的是 `MediaTypeHandler`（非 undefined），不再需要 `!` 断言。
+   * 仅给「确定 type 在表里」的调用方用 —— image/file/voice/video 四类入口；通用 dispatcher 仍可用 `mediaTypeHandlers[type]?.` optional chain
+   */
+  const requireMediaHandler = (type: number): MediaTypeHandler => {
+    const handler = mediaTypeHandlers[type]
+    if (!handler) {
+      throw new Error(`[IM] 未注册的媒体类型 ${type}`)
+    }
+    return handler
+  }
+
   /**
    * 上传完成后的收口校验：会话仍是占位时锁定的那个 + 当前未被禁言；任一不满足 markMediaFailed + 返回 false
    *
@@ -317,6 +331,7 @@ export const useMediaUploader = () => {
     commitMediaPlaceholder,
     createUploadProgressHandler,
     verifyMediaUploadStillAllowed,
-    getMediaKind
+    getMediaKind,
+    requireMediaHandler
   }
 }

src/views/im/home/pages/conversation/components/input/MessageInput.vue

@@ -170,10 +170,7 @@ import { useFriendStore } from '@/views/im/home/store/friendStore'
 import { useDraftStore } from '@/views/im/home/store/draftStore'
 import { getMemberDisplayName } from '@/views/im/utils/user'
 import { useMessageSender } from '@/views/im/home/composables/useMessageSender'
-import {
-  mediaTypeHandlers,
-  useMediaUploader
-} from '@/views/im/home/composables/useMediaUploader'
+import { useMediaUploader } from '@/views/im/home/composables/useMediaUploader'
 import { useMuteOverlay } from '@/views/im/home/composables/useMuteOverlay'
 import { getConversationKey } from '@/views/im/utils/conversation'
 import { ImConversationType, ImMessageType } from '@/views/im/utils/constants'
@@ -203,7 +200,8 @@ const {
   markMediaFailed,
   commitMediaPlaceholder,
   createUploadProgressHandler,
-  verifyMediaUploadStillAllowed
+  verifyMediaUploadStillAllowed,
+  requireMediaHandler
 } = useMediaUploader()
 
 const editorRef = useTemplateRef<HTMLDivElement>('editorRef')
@@ -997,13 +995,13 @@ async function uploadAndSendVideo(file: File) {
   const replyQuote = context.quote
   const startKey = getConversationKey(conversation)
 
-  // 1. 立即占位：blob URL 同时作 url + coverUrl 让 <video> 渲染首帧；_localFile 留 file 供失败重试
+  // 1. 立即占位：url 走 blob 让 <video src> 拉首字节渲染；coverUrl 不设 blob
+  //    （<video poster> 期待图片资源，传 video blob 在部分浏览器会退化成黑底，不是稳定行为）
+  //    cover 等 probe 异步出真实 URL 后由 commit 阶段一起 patch；_localFile 留 file 供失败重试
   //    payload 拼装走 mediaTypeHandlers[VIDEO].build 与 commit 阶段共享同一份逻辑
-  const videoHandler = mediaTypeHandlers[ImMessageType.VIDEO]!
+  const videoHandler = requireMediaHandler(ImMessageType.VIDEO)
   const buildPlaceholderContent = (blobUrl: string): string =>
-    serializeMessage(
-      withQuotePayload(videoHandler.build(file, blobUrl, { videoCoverUrl: blobUrl }), replyQuote)
-    )
+    serializeMessage(withQuotePayload(videoHandler.build(file, blobUrl, {}), replyQuote))
   const { clientMessageId } = insertMediaPlaceholder({
     file,
     type: ImMessageType.VIDEO,

src/views/im/home/pages/conversation/components/message/MessageItem.vue

@@ -193,10 +193,8 @@
         <!-- 状态区：自己消息展示发送状态 + 已读/群回执；对方消息 + @自己时展示 @徽标 -->
         <div class="flex gap-1.5 items-center text-base">
           <template v-if="message.selfSend">
-            <!-- SENDING 显示外层 loading；图片/视频/文件气泡自身有进度反馈则抑制；
-                 语音气泡只有麦克风 + 时长，无内嵌进度条，必须保留外层 loading 让用户感知正在发送 -->
             <Icon
-              v-if="message.status === ImMessageStatus.SENDING && (!isUploading || isVoice)"
+              v-if="showSendingLoading"
               icon="ant-design:loading-outlined"
               class="im-loading-spin"
             />
@@ -506,6 +504,16 @@ const uploadProgress = computed(() => props.message.uploadProgress ?? 0)
 /** 上传进度文案；图片/视频遮罩、文件进度条尾巴共用 */
 const uploadProgressText = computed(() => `${uploadProgress.value}%`)
 
+/**
+ * 是否在气泡尾部显示「发送中」loading 转圈
+ *
+ * 图片 / 视频 / 文件气泡内嵌已有进度反馈（遮罩 / 进度条），外层 loading 多余则抑制；
+ * 语音气泡只有麦克风 + 时长，无内嵌进度，必须保留外层 loading 让用户感知正在发送
+ */
+const showSendingLoading = computed(
+  () => props.message.status === ImMessageStatus.SENDING && (!isUploading.value || isVoice.value)
+)
+
 /** 文件类型图标 + 配色：按扩展名分发，跟 ReplyPreview 共用 getFileIconInfo */
 const fileIconInfo = computed(() => getFileIconInfo(filePayload.value?.name))
 

src/views/im/home/store/conversationStore.ts

@@ -91,6 +91,8 @@ function recomputeConversationLast(conversation: Conversation): void {
     conversation.lastMessageType = undefined
     conversation.lastSelfSend = undefined
     conversation.lastSenderDisplayName = undefined
+    // 排序时间也要清，否则空会话仍按旧 lastSendTime 排在前面（刷新后媒体占位被 drop 时容易踩到）
+    conversation.lastSendTime = 0
   }
 }