test: add Playwright e2e tests for new features and uncovered workflows

High priority (new PR #108 features):
- Command palette: open/close, search flows, page navigation, FlowPilot handoff
- Fallback branches: add in editor, execute in session runner
- Session-to-flow: verify button appears on completed session detail

Medium priority (existing features without coverage):
- Procedural session: intake form, step-through, completion
- Tree editor: troubleshooting and procedural editor load/edit/save
- FlowPilot chat: page load, new chat creation
- Admin panel: dashboard, user management, settings access

Also adds API helpers: createProceduralTree(), createProceduralTreeWithFallbacks()

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/e2e/flowpilot-chat.spec.ts

@@ -0,0 +1,34 @@
+import { expect, test } from '@playwright/test'
+
+test.describe('FlowPilot assistant chat smoke tests', () => {
+  test('can open the assistant chat page and see the chat interface', async ({ page }) => {
+    await page.goto('/assistant')
+
+    // Should load the assistant chat page
+    await expect(page.getByText(/FlowPilot|Assistant|Chat/i)).toBeVisible({ timeout: 10000 })
+
+    // Should have an input area for sending messages
+    const messageInput = page.getByPlaceholder(/message|ask|type/i)
+    await expect(messageInput).toBeVisible()
+  })
+
+  test('can create a new chat session', async ({ page }) => {
+    await page.goto('/assistant')
+    await expect(page.getByText(/FlowPilot|Assistant|Chat/i)).toBeVisible({ timeout: 10000 })
+
+    // Look for new chat button
+    const newChatButton = page.getByRole('button', { name: /New|Create/i }).first()
+    if (await newChatButton.isVisible()) {
+      await newChatButton.click()
+
+      // Should be able to type a message
+      const messageInput = page.getByPlaceholder(/message|ask|type/i)
+      await expect(messageInput).toBeVisible()
+      await messageInput.fill('How do I troubleshoot DNS issues?')
+    }
+  })
+
+  // Note: Full AI response tests require ANTHROPIC_API_KEY in the environment.
+  // The send-and-receive flow is validated by the command palette prefill test
+  // which navigates here with a prefilled message.
+})