feat(e2e): consolidate E2E infra + add waitForSidebar (PRI-698) (#42)

* 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

* fix(e2e): add @playwright/test to devDependencies and e2e script (PRI-698)

@playwright/test was missing from devDependencies, causing the
'Install Playwright browsers' step to fail. Added it alongside
the e2e npm script so the reusable workflow can run playwright test.

* fix(e2e): reference @main workflow after .github merge

Co-Authored-By: Paperclip <noreply@paperclip.ing>

---------

Co-authored-by: Chris Farhood <chris@farhood.org>
Co-authored-by: Paperclip <noreply@paperclip.ing>

package.json

@@ -23,7 +23,8 @@
     "format": "prettier --write src/",
     "format:check": "prettier --check src/",
     "test": "vitest run",
-    "test:watch": "vitest"
+    "test:watch": "vitest",
+    "e2e": "playwright test"
   },
   "peerDependencies": {
     "react": "^18.0.0",
@@ -46,7 +47,8 @@
     "react-dom": "^18.3.1",
     "react-router-dom": "^5.3.0",
     "typescript": "~5.6.2",
-    "vitest": "^3.2.4"
+    "vitest": "^3.2.4",
+    "@playwright/test": "^1.59.1"
   },
   "overrides": {
     "tar": "^7.5.11",