BottleBackend.prepare computed slug and resolved_env but never passed
them to _resolve_plan. The concrete docker/smolmachines _resolve_plan
methods still had the old (spec, *, stage_dir) signature too, so
prepare's kwargs blew up with "unexpected keyword argument
'instance_name'" the moment cli.py start was invoked.
Update the abstract _resolve_plan signature and both backend
implementations to accept the full kwarg set prepare passes, and
forward to resolve_plan.resolve_plan() with everything.
didericis-claude
bb8c2291bd