test(I2): vitest component smoke tests for high-risk UI

Adds @vue/test-utils + happy-dom and mounts CredentialCard, DownloadEventRow,
PostCard, ActiveDownloadsPanel, QueueStatusBar, asserting they render without
throwing and surface key content — catching the dead-binding / render-error
class (e.g. the last_verified_at regression, guarded explicitly). Vuetify
components are left unresolved (Vue renders unknown elements + slots), so no
Vuetify-plugin setup is needed; only RouterLink is stubbed. Per-file
happy-dom env via docblock keeps the existing node-env specs untouched.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/test/components/queueStatusBar.spec.js

@@ -0,0 +1,26 @@
+// @vitest-environment happy-dom
+import { describe, it, expect } from 'vitest'
+
+import QueueStatusBar from '../../src/components/settings/QueueStatusBar.vue'
+import { useSystemActivityStore } from '../../src/stores/systemActivity.js'
+import { freshPinia, mountComponent } from '../support/mountComponent.js'
+
+describe('QueueStatusBar', () => {
+  it('shows the pending count when the queue is busy', () => {
+    const pinia = freshPinia()
+    useSystemActivityStore().queues = { queues: { ml: 3 }, fetched_at: '' }
+    const w = mountComponent(QueueStatusBar, {
+      props: { queue: 'ml', queueLabel: 'ML' }, pinia,
+    })
+    expect(w.text()).toContain('3 pending')
+  })
+
+  it('reads idle when the queue is empty', () => {
+    const pinia = freshPinia()
+    useSystemActivityStore().queues = { queues: { ml: 0 }, fetched_at: '' }
+    const w = mountComponent(QueueStatusBar, {
+      props: { queue: 'ml', queueLabel: 'ML' }, pinia,
+    })
+    expect(w.text().toLowerCase()).toContain('idle')
+  })
+})