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/activeDownloadsPanel.spec.js

@@ -0,0 +1,30 @@
+// @vitest-environment happy-dom
+import { describe, it, expect } from 'vitest'
+
+import ActiveDownloadsPanel from '../../src/components/subscriptions/ActiveDownloadsPanel.vue'
+import { useDownloadsStore } from '../../src/stores/downloads.js'
+import { freshPinia, mountComponent } from '../support/mountComponent.js'
+
+describe('ActiveDownloadsPanel', () => {
+  it('lists a running download with its artist', () => {
+    const pinia = freshPinia()
+    useDownloadsStore().activeEvents = [{
+      id: 1, status: 'running',
+      started_at: new Date(Date.now() - 65000).toISOString(),
+      platform: 'patreon', artist_name: 'Alice',
+    }]
+    const w = mountComponent(ActiveDownloadsPanel, { pinia })
+    const t = w.text()
+    expect(t).toContain('Alice')
+    expect(t).toContain('downloading')
+    w.unmount() // clear the 1s elapsed-timer interval
+  })
+
+  it('renders nothing when there is no active work', () => {
+    const pinia = freshPinia()
+    useDownloadsStore().activeEvents = []
+    const w = mountComponent(ActiveDownloadsPanel, { pinia })
+    expect(w.text()).toBe('')
+    w.unmount()
+  })
+})