docs: enhance E2E testing with comprehensive docs and new tests

Add comprehensive Playwright E2E testing documentation and additional
test coverage for app bar badge and plugin settings functionality.

Changes:
- Add GitHub Actions workflow for E2E tests (.github/workflows/e2e.yaml)
- Create .env.example for local test configuration
- Update .gitignore to exclude .env files
- Enhance e2e/README.md with:
  - Detailed test coverage documentation
  - Cluster requirements and prerequisites
  - Debugging guides and troubleshooting tips
  - CI/CD integration instructions for GitHub Actions
  - Best practices and examples for writing new tests
- Add e2e/settings.spec.ts:
  - Test plugin settings page visibility
  - Test refresh interval configuration
  - Test dashboard URL configuration
  - Test connection test button
- Add e2e/appbar.spec.ts:
  - Test badge displays cluster score
  - Test badge navigation to overview
  - Test badge color reflects score level
  - Test badge updates across clusters

Test Results (v0.3.4):
- 5/16 tests passing (sidebar, namespaces, drawer functionality)
- 11/16 failing due to missing v0.3.4 features (settings, app bar badge)
- Tests will pass once plugin is updated to v0.3.4 in cluster

The E2E test suite now provides comprehensive coverage of:
- Plugin registration and loading
- Navigation and routing
- Settings configuration
- App bar integration
- Dark mode support
- Data fetching and rendering

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

e2e/appbar.spec.ts

@@ -0,0 +1,94 @@
+import { test, expect } from '@playwright/test';
+
+test.describe('Polaris app bar badge', () => {
+  test('badge displays cluster score in app bar', async ({ page }) => {
+    await page.goto('/c/main');
+
+    // Wait for page to load
+    await expect(page.getByRole('navigation', { name: 'Navigation' })).toBeVisible();
+
+    // Badge should be visible in app bar with score percentage
+    const badge = page.getByRole('button', { name: /Polaris: \d+%/ });
+    await expect(badge).toBeVisible({ timeout: 15_000 });
+
+    // Badge should show shield emoji
+    await expect(badge).toContainText('🛡️');
+  });
+
+  test('clicking badge navigates to overview page', async ({ page }) => {
+    await page.goto('/c/main');
+
+    // Find and click the badge
+    const badge = page.getByRole('button', { name: /Polaris: \d+%/ });
+    await expect(badge).toBeVisible({ timeout: 15_000 });
+    await badge.click();
+
+    // Should navigate to Polaris overview
+    await expect(page).toHaveURL(/\/c\/main\/polaris$/);
+    await expect(page.getByRole('heading', { name: 'Polaris — Overview' })).toBeVisible();
+  });
+
+  test('badge color reflects score level', async ({ page }) => {
+    await page.goto('/c/main');
+
+    // Get the badge
+    const badge = page.getByRole('button', { name: /Polaris: \d+%/ });
+    await expect(badge).toBeVisible({ timeout: 15_000 });
+
+    // Extract score from button text
+    const badgeText = await badge.textContent();
+    const scoreMatch = badgeText?.match(/(\d+)%/);
+    expect(scoreMatch).toBeTruthy();
+
+    const score = parseInt(scoreMatch![1]);
+
+    // Check background color matches score level
+    const bgColor = await badge.evaluate(el =>
+      window.getComputedStyle(el).backgroundColor
+    );
+
+    if (score >= 80) {
+      // Green: rgb(76, 175, 80) or #4caf50
+      expect(bgColor).toMatch(/rgb\(76,\s*175,\s*80\)/);
+    } else if (score >= 50) {
+      // Orange: rgb(255, 152, 0) or #ff9800
+      expect(bgColor).toMatch(/rgb\(255,\s*152,\s*0\)/);
+    } else {
+      // Red: rgb(244, 67, 54) or #f44336
+      expect(bgColor).toMatch(/rgb\(244,\s*67,\s*54\)/);
+    }
+  });
+
+  test('badge updates when navigating between clusters', async ({ page }) => {
+    // This test assumes multi-cluster setup; skip if only one cluster
+    await page.goto('/c/main');
+
+    // Get initial badge score
+    const badge = page.getByRole('button', { name: /Polaris: \d+%/ });
+    await expect(badge).toBeVisible({ timeout: 15_000 });
+    const initialScore = await badge.textContent();
+
+    // Try to switch clusters (if available)
+    const clusterSelector = page.getByRole('button', { name: /cluster/i });
+    if (await clusterSelector.isVisible()) {
+      // Note: This part will only work in multi-cluster setups
+      // For single-cluster, this test will just verify badge persists
+      await clusterSelector.click();
+
+      // Select different cluster if available
+      const clusterOptions = page.getByRole('menuitem');
+      const count = await clusterOptions.count();
+
+      if (count > 1) {
+        await clusterOptions.nth(1).click();
+
+        // Badge should update or disappear (if new cluster doesn't have Polaris)
+        // This is just verifying no crash occurs
+        await page.waitForTimeout(2000);
+      }
+    }
+
+    // Badge should still be functional
+    await expect(badge).toBeEnabled();
+  });
+});