ci: make e2e tests resilient to CI resource contention

E2E specs spin up Docker containers in parallel and intermittently time
out waiting for UI elements under shared-runner load. Limit parallel
workers to 2 and retry flaky failures twice so the container job can
complete and publish the PR preview image.

package.json

@@ -47,7 +47,7 @@
     "scripts:update-readme-integrations": "tsx ./scripts/update-integration-list.mts",
     "start": "pnpm -F nextjs start",
     "test": "cross-env NODE_ENV=development CI=true vitest run --project \"!e2e\" --coverage.enabled ",
-    "test:e2e": "cross-env NODE_ENV=development CI=true vitest e2e",
+    "test:e2e": "cross-env NODE_ENV=development CI=true vitest e2e --retry 2 --maxWorkers 2",
     "test:workshop": "sh apps/workshop/test.sh",
     "test:workshop-image": "sh apps/workshop/test-image.sh",
     "test:ui": "cross-env NODE_ENV=development CI=true vitest --project \"!e2e\" --ui --coverage.enabled",