feat(e2e): consolidate E2E test infrastructure + add waitForSidebar (PRI-698)

- Adds e2e/auth.setup.ts, e2e/tns-csi.spec.ts with waitForSidebar helper
- Adds playwright.config.ts, scripts/deploy-e2e-headlamp.sh, scripts/teardown-e2e-headlamp.sh
- Adds .github/workflows/e2e.yaml
- Plugin settings test waits for list before searching

playwright.config.ts

@@ -0,0 +1,27 @@
+import { defineConfig, devices } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './e2e',
+  timeout: 30_000,
+  expect: { timeout: 10_000 },
+  fullyParallel: false,
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 1 : 0,
+  reporter: 'list',
+  use: {
+    baseURL: process.env.HEADLAMP_URL || (() => { throw new Error('HEADLAMP_URL is required — run scripts/deploy-e2e-headlamp.sh first'); })(),
+    trace: 'on-first-retry',
+    screenshot: 'only-on-failure',
+  },
+  projects: [
+    { name: 'setup', testMatch: /auth\.setup\.ts/, timeout: 60_000 },
+    {
+      name: 'chromium',
+      use: {
+        ...devices['Desktop Chrome'],
+        storageState: 'e2e/.auth/state.json',
+      },
+      dependencies: ['setup'],
+    },
+  ],
+});