feat(frontend): 完善主题导入与手帐工作区并修复 Mermaid 预览

frontend/src/features/editor/codeBlockLabels.spec.ts

@@ -0,0 +1,18 @@
+// @vitest-environment happy-dom
+import { expect, it } from 'vitest'
+import { installCodeBlockLabels } from './codeBlockLabels'
+
+it('keeps footer labels in sync when the language changes and stops after disposal', async () => {
+  const root = document.createElement('div')
+  root.innerHTML = '<div class="milkdown-code-block"><button class="language-button">Python</button></div>'
+  const dispose = installCodeBlockLabels(root)
+  const block = root.firstElementChild as HTMLElement
+  expect(block.dataset.languageLabel).toBe('Python')
+  block.querySelector('button')!.textContent = 'TypeScript'
+  await new Promise(resolve => setTimeout(resolve, 0))
+  expect(block.dataset.languageLabel).toBe('TypeScript')
+  dispose()
+  block.querySelector('button')!.textContent = 'Rust'
+  await new Promise(resolve => setTimeout(resolve, 0))
+  expect(block.dataset.languageLabel).toBe('TypeScript')
+})