'incus admin init --minimal' picks the 'dir' backend, which has no
copy-on-write: every snapshot and clone is a full copy of the box's
root — several GB and minutes apiece once Docker, Node and Claude Code
are installed. Measured live: one clone took minutes, and a single
drill run pays that three times (snapshot + two clones). The workflow
the tool exists for — log in once, snapshot, clone forever — stops
being attractive at exactly that price.
setup-host.sh now bootstraps via a preseed that mirrors what --minimal
creates (default pool, incusbr0, default profile with root + eth0) with
only the driver deliberate: btrfs on a loop device (CoW — clones share
blocks and diverge on write), installing btrfs-progs if absent, falling
back to dir with a warning if btrfs cannot be had. Existing hosts are
untouched: the block is skipped whenever a 'default' pool exists.
Closes#29
