Decompose the 207-line launch() into six named helpers: _allocate_resources,
_mint_certs, _start_bundle, _discover_urls, _launch_vm, _init_vm. Each has
explicit inputs/outputs and is independently testable.
Replace time.sleep(1.5) with smolvm.wait_exec_ready(), which polls
`machine exec true` with exponential backoff. Exits as soon as the exec
channel is ready; dies loudly with a timeout message instead of silently
leaving the VM in an unknown state.
File-lock loopback_alias.allocate() with fcntl.flock(LOCK_EX) so concurrent
bottle launches can't race on docker state and claim the same alias.