Linux boots on Kern's hypervisor

The container engine now extends beyond Linux namespaces. On macOS, Kern boots a full Linux kernel via Apple's Virtualization.framework: ARM64 with GIC emulation, virtiofs file sharing, and virtio-console. Multi-container lifecycle works on macOS: cgroups v2, NAT networking, log capture, and port forwarding, all running inside the VM. On Linux, containers run directly via namespaces as before. Production deploys still need only the Kern binary + Linux kernel 5.15+ + libc, but development on macOS now runs real Linux containers without Docker Desktop.