feat: Add seed command support to preview deployments

Run project-specific initialization commands (DB migrations, fixture
loading, etc.) automatically after containers are healthy, before the
preview is marked ready. Configured via per-service `seed` arrays in
.cw-preview.yml.

apps/server/preview/manager.test.ts

@@ -10,6 +10,7 @@ vi.mock('./docker-client.js', () => ({
   isDockerAvailable: vi.fn(),
   composeUp: vi.fn(),
   composeDown: vi.fn(),
+  execInContainer: vi.fn(),
   composePs: vi.fn(),
   listPreviewProjects: vi.fn(),
   getContainerLabels: vi.fn(),
@@ -74,6 +75,7 @@ import {
   isDockerAvailable,
   composeUp,
   composeDown,
+  execInContainer,
   composePs,
   listPreviewProjects,
   getContainerLabels,
@@ -91,6 +93,7 @@ const mockComposeDown = vi.mocked(composeDown);
 const mockComposePs = vi.mocked(composePs);
 const mockListPreviewProjects = vi.mocked(listPreviewProjects);
 const mockGetContainerLabels = vi.mocked(getContainerLabels);
+const mockExecInContainer = vi.mocked(execInContainer);
 const mockDiscoverConfig = vi.mocked(discoverConfig);
 const mockAllocatePort = vi.mocked(allocatePort);
 const mockWaitForHealthy = vi.mocked(waitForHealthy);
@@ -302,6 +305,76 @@ describe('PreviewManager', () => {
       expect(failedEvent).toBeDefined();
     });
 
+    it('runs seed commands after health check and before preview:ready', async () => {
+      const seededConfig: PreviewConfig = {
+        version: 1,
+        services: {
+          app: {
+            name: 'app',
+            build: '.',
+            port: 3000,
+            seed: ['npm run db:migrate', 'npm run db:seed'],
+          },
+        },
+      };
+
+      mockIsDockerAvailable.mockResolvedValue(true);
+      mockComposeUp.mockResolvedValue(undefined);
+      mockComposePs.mockResolvedValue([{ name: 'app', state: 'running', health: 'healthy' }]);
+      mockDiscoverConfig.mockResolvedValue(seededConfig);
+      mockCreatePreviewWorktree.mockResolvedValue(undefined);
+      mockWaitForHealthy.mockResolvedValue([{ name: 'app', healthy: true }]);
+      mockExecInContainer.mockResolvedValue({ stdout: '', stderr: '' });
+
+      const result = await manager.start({
+        initiativeId: 'init-1',
+        projectId: 'proj-1',
+        branch: 'feature-x',
+      });
+
+      expect(result.status).toBe('running');
+      expect(mockExecInContainer).toHaveBeenCalledTimes(2);
+      expect(mockExecInContainer).toHaveBeenCalledWith('cw-preview-abc123test', 'app', 'npm run db:migrate');
+      expect(mockExecInContainer).toHaveBeenCalledWith('cw-preview-abc123test', 'app', 'npm run db:seed');
+
+      const readyEvent = eventBus.emitted.find((e) => e.type === 'preview:ready');
+      expect(readyEvent).toBeDefined();
+    });
+
+    it('emits preview:failed and cleans up when seed command fails', async () => {
+      const seededConfig: PreviewConfig = {
+        version: 1,
+        services: {
+          app: {
+            name: 'app',
+            build: '.',
+            port: 3000,
+            seed: ['npm run db:migrate'],
+          },
+        },
+      };
+
+      mockIsDockerAvailable.mockResolvedValue(true);
+      mockComposeUp.mockResolvedValue(undefined);
+      mockDiscoverConfig.mockResolvedValue(seededConfig);
+      mockCreatePreviewWorktree.mockResolvedValue(undefined);
+      mockWaitForHealthy.mockResolvedValue([{ name: 'app', healthy: true }]);
+      mockExecInContainer.mockRejectedValue(new Error('migration failed: relation already exists'));
+      mockComposeDown.mockResolvedValue(undefined);
+
+      await expect(
+        manager.start({
+          initiativeId: 'init-1',
+          projectId: 'proj-1',
+          branch: 'main',
+        }),
+      ).rejects.toThrow('Preview build failed');
+
+      const failedEvent = eventBus.emitted.find((e) => e.type === 'preview:failed');
+      expect(failedEvent).toBeDefined();
+      expect(mockComposeDown).toHaveBeenCalled();
+    });
+
     it('succeeds when no healthcheck endpoints are configured', async () => {
       const noHealthConfig: PreviewConfig = {
         version: 1,