- `banger vm prune` sweeps every non-running VM (stopped, created,
error) with an interactive confirmation; -f/--force skips the prompt.
Partial failures report which VM failed and exit non-zero.
- list commands gain `ls` alias: vm list already had it; added to image
list, kernel list, and vm session list.
- delete commands gain `rm` alias: vm delete and image delete. kernel
rm already aliased delete/remove.
Uses new test seams (vmListFunc) plus the existing vmDeleteFunc so
prune unit-tests without touching the daemon socket.
