test: add Playwright smoke test for canary release settings

Verifies update channel dropdown renders in Settings, defaults to
stable, and persists canary selection across settings panel open/close.

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

tests/smoke/canary-release-feature-flags.spec.ts

@@ -0,0 +1,48 @@
+import { test, expect } from '@playwright/test'
+import { openCommandPalette, executeCommand } from './helpers'
+
+async function openSettings(page: import('@playwright/test').Page) {
+  await openCommandPalette(page)
+  await executeCommand(page, 'Settings')
+  const panel = page.locator('[data-testid="settings-panel"]')
+  await panel.waitFor({ timeout: 5000 })
+  return panel
+}
+
+test.describe('Canary release channel + feature flags', () => {
+  test.beforeEach(async ({ page }) => {
+    await page.goto('/')
+    await page.waitForLoadState('networkidle')
+  })
+
+  test('Settings panel shows Update channel dropdown defaulting to Stable', async ({ page }) => {
+    await openSettings(page)
+
+    // Check the Updates section exists
+    await expect(page.getByText('Updates')).toBeVisible()
+    await expect(page.getByText('Canary builds include')).toBeVisible()
+
+    // Check the dropdown defaults to stable
+    const select = page.locator('[data-testid="settings-update-channel"]')
+    await expect(select).toBeVisible()
+    await expect(select).toHaveValue('stable')
+  })
+
+  test('Update channel can be changed to canary and saved', async ({ page }) => {
+    await openSettings(page)
+
+    // Change to canary
+    const select = page.locator('[data-testid="settings-update-channel"]')
+    await select.selectOption('canary')
+    await expect(select).toHaveValue('canary')
+
+    // Save (closes the panel)
+    await page.click('[data-testid="settings-save"]')
+    await page.waitForTimeout(500)
+
+    // Reopen settings and verify the value persisted
+    await openSettings(page)
+    const reopenedSelect = page.locator('[data-testid="settings-update-channel"]')
+    await expect(reopenedSelect).toHaveValue('canary')
+  })
+})