fix(e2e): harden card selectors for session resume

Co-Authored-By: Codex <noreply@openai.com>

frontend/e2e/resume.spec.ts

@@ -28,7 +28,7 @@ test.describe('session resume smoke tests', () => {
       await page.getByRole('button', { name: 'Flow Sessions' }).click()
       // Active sub-tab is the default and surfaces in-progress sessions.
 
-      const resumeCard = page.locator('.bg-card').filter({ hasText: tree.name }).first()
+      const resumeCard = page.getByTestId('flow-session-card').filter({ hasText: tree.name }).first()
       await expect(resumeCard).toBeVisible()
       await resumeCard.getByRole('button', { name: 'Resume' }).first().click()