feat(home): add AI story expand button and modal

tests/unit/home/ai-story-expand.test.ts

@@ -0,0 +1,50 @@
+import { describe, expect, it, vi } from 'vitest'
+import { expandHomeStory } from '@/lib/home/ai-story-expand'
+
+vi.mock('@/lib/task/client', () => ({
+  resolveTaskResponse: vi.fn(),
+}))
+
+import { resolveTaskResponse } from '@/lib/task/client'
+
+function buildJsonResponse(body: unknown, status = 200): Response {
+  return new Response(JSON.stringify(body), {
+    status,
+    headers: { 'Content-Type': 'application/json' },
+  })
+}
+
+describe('expandHomeStory', () => {
+  it('posts the prompt to the user ai-story-expand route and returns expanded text', async () => {
+    const apiFetch = vi.fn(async () => buildJsonResponse({ async: true, taskId: 'task-1' }))
+    vi.mocked(resolveTaskResponse).mockResolvedValue({
+      expandedText: '扩写后的故事正文',
+    })
+
+    const result = await expandHomeStory({
+      apiFetch,
+      prompt: '宫廷复仇女主回京',
+    })
+
+    expect(apiFetch).toHaveBeenCalledWith('/api/user/ai-story-expand', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({
+        prompt: '宫廷复仇女主回京',
+      }),
+    })
+    expect(result).toEqual({
+      expandedText: '扩写后的故事正文',
+    })
+  })
+
+  it('fails explicitly when the route does not return expandedText', async () => {
+    const apiFetch = vi.fn(async () => buildJsonResponse({ async: true, taskId: 'task-1' }))
+    vi.mocked(resolveTaskResponse).mockResolvedValue({})
+
+    await expect(expandHomeStory({
+      apiFetch,
+      prompt: '宫廷复仇女主回京',
+    })).rejects.toThrow('AI story expand response missing expandedText')
+  })
+})

tests/unit/home/quick-start-textarea.test.ts

@@ -59,6 +59,10 @@ vi.mock('@/lib/home/create-project-launch', () => ({
   createHomeProjectLaunch: vi.fn(),
 }))
 
+vi.mock('@/lib/home/ai-story-expand', () => ({
+  expandHomeStory: vi.fn(),
+}))
+
 describe('resolveTextareaTargetHeight', () => {
   it('keeps the home quick-start input at least three rows tall', () => {
     expect(resolveTextareaTargetHeight({