fix: 切换会话时重置 dockView

新增对 selected 的监听，切换会话时清空 dockView；更新 v0.4.4 验证截图

src/client/views/ConversationsView.vue

@@ -887,6 +887,7 @@ watch([selected,selectedTask], () => {
   pendingRequestId = undefined;uploadedSources = [];uploadedReferences = []
   void load()
 })
+watch(selected,()=>{dockView.value=undefined})
 watch(() => auth.user?.id, (owner, previous) => {
   if (owner === previous) return
   knowledgePanel.value?.close(); knowledgeEnabled.value = false; projects.value = []; knowledgeRevision.value++