fix(e2e): add full E2E infrastructure (workflow, scripts, tests)

- Copy deploy/teardown scripts from add-e2e-infra branch
- Copy Playwright config and test files
- Add e2e script and @playwright/test devDependency
- Update E2E workflow to use pnpm-capable workflow branch with namespace param

PRI-634 follow-up

e2e/argocd.spec.ts

@@ -0,0 +1,42 @@
+import { test, expect } from '@playwright/test';
+
+test.describe('argocd plugin smoke tests', () => {
+  test('sidebar contains argocd entry', async ({ page }) => {
+    await page.goto('/');
+    const sidebar = page.getByRole('navigation', { name: 'Navigation' });
+    await expect(sidebar).toBeVisible({ timeout: 15_000 });
+    await expect(sidebar.getByRole('button', { name: /argocd/i })).toBeVisible();
+  });
+
+  test('argocd sidebar entry navigates to argocd view', async ({ page }) => {
+    await page.goto('/');
+    const sidebar = page.getByRole('navigation', { name: 'Navigation' });
+    await expect(sidebar).toBeVisible({ timeout: 15_000 });
+
+    const entry = sidebar.getByRole('button', { name: /argocd/i });
+    await expect(entry).toBeVisible();
+    await entry.click();
+
+    await expect(page).toHaveURL(/argocd/);
+    await expect(page.getByRole('heading', { name: /argocd/i })).toBeVisible();
+  });
+
+  test('argocd page renders content', async ({ page }) => {
+    await page.goto('/c/main/argocd');
+
+    await expect(page.getByRole('heading', { name: /argocd/i })).toBeVisible({
+      timeout: 15_000,
+    });
+
+    const hasTable = await page.locator('table').first().isVisible().catch(() => false);
+    const hasContent = await page.locator('[class*="Mui"]').first().isVisible().catch(() => false);
+    expect(hasTable || hasContent).toBe(true);
+  });
+
+  test('plugin settings page shows argocd plugin entry', async ({ page }) => {
+    await page.goto('/settings/plugins');
+
+    const pluginEntry = page.locator('text=/argocd/i').first();
+    await expect(pluginEntry).toBeVisible({ timeout: 30_000 });
+  });
+});