test: align smoke fixtures with runtime constraints

[chimerakang]

Summary

• raise smoke/e2e Pod memory requests and limits to 256Mi to satisfy apple/container VM minimums
• switch multi-node e2e default image to busybox:1.36.1 because the harness needs sh, httpd, and wget

Validation

• go test ./...
• golangci-lint run
• make build
• local kind-backed smoke covered node registration, Pod Ready, logs, exec, emptyDir, port-forward, metrics, image-arch failure, and cleanup