feat: parallel agent upgrades with per-host log panels (0.4.2)

Allow multiple remote update jobs at once; each upgrade gets its own
bottom-right log dock that auto-closes 30s after success.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/App.vue

@@ -4,16 +4,7 @@
     <main :class="showShell ? 'app-main' : ''">
       <RouterView />
     </main>
-    <HostActionLogModal
-      v-if="showShell"
-      :open="hostRemoteActionLog.open"
-      :title="hostRemoteActionLog.title"
-      :loading="hostRemoteActionLog.loading"
-      :ok="hostRemoteActionLog.ok"
-      :message="hostRemoteActionLog.message"
-      :output="hostRemoteActionLog.output"
-      @close="closeHostRemoteActionLog"
-    />
+    <HostActionLogStack v-if="showShell" />
   </div>
 </template>
 
@@ -22,11 +13,7 @@ import { computed, onMounted } from "vue";
 import { useRoute } from "vue-router";
 import { getToken } from "./api";
 import AppSidebar from "./components/AppSidebar.vue";
-import HostActionLogModal from "./components/HostActionLogModal.vue";
-import {
-  closeHostRemoteActionLog,
-  hostRemoteActionLog,
-} from "./composables/useHostRemoteAction";
+import HostActionLogStack from "./components/HostActionLogStack.vue";
 import { refreshSessionRole } from "./router";
 
 const route = useRoute();