Compares smolmachines against the six subsystems in
agent-vm-isolation.md. smolmachines replaces the microVM runtime,
network attachment (libkrun TSI with built-in DNS-over-vsock filter),
vsock control plane, and Python lifecycle wrapper. Pipelock stays;
disk-image story shifts to OCI + writable overlay. Recommends adopting
smolmachines as the macOS VM backend after smoke-testing TSI
passthrough to a host-side pipelock.