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/components/HostActionLogStack.vue

@@ -0,0 +1,49 @@
+<template>
+  <div v-if="openLogs.length" class="host-action-log-stack" aria-live="polite">
+    <HostActionLogModal
+      v-for="entry in openLogs"
+      :key="entry.id"
+      :open="true"
+      :title="entry.title"
+      :loading="entry.loading"
+      :ok="entry.ok"
+      :message="entry.message"
+      :output="entry.output"
+      @close="closeHostRemoteActionLog(entry.id)"
+    />
+  </div>
+</template>
+
+<script setup lang="ts">
+import { computed } from "vue";
+import HostActionLogModal from "./HostActionLogModal.vue";
+import {
+  closeHostRemoteActionLog,
+  hostRemoteActionLogs,
+} from "../composables/useHostRemoteAction";
+
+const openLogs = computed(() => hostRemoteActionLogs.filter((e) => e.open));
+</script>
+
+<style scoped>
+.host-action-log-stack {
+  position: fixed;
+  right: 1rem;
+  bottom: 1rem;
+  z-index: 1000;
+  display: flex;
+  flex-direction: column-reverse;
+  align-items: flex-end;
+  gap: 0.65rem;
+  width: min(56rem, calc(100vw - 2rem));
+  max-height: min(90vh, 48rem);
+  overflow-y: auto;
+  pointer-events: none;
+}
+
+.host-action-log-stack :deep(.host-action-log-panel) {
+  pointer-events: auto;
+  width: 100%;
+  max-height: min(36rem, 45vh);
+}
+</style>