Moving a subnet between fabrics does NOT bring interface links along. The
first apply created vr1-dc0-provider-public and moved 10.12.4.0/22 onto it,
leaving the region VM's enp2s0 holding a static 10.12.4.6 on a VLAN whose
subnet had left -- the region's provider-public leg, which it needs for
image sync, and the same under-carve class that cost three bootstrap
attempts on the Juju controller. Live connectivity was unaffected because
the OS netplan is independent of MAAS's model, so every other assertion
passed 39/39 with the model inconsistent.

Renaming the auto fabric that already carries the subnet moves nothing. A
MOVE is kept only for the case where the fabric carries other planes, and
now prints a warning that links do not follow.

Adds the assertion that would have caught it: every interface link must be
on its subnet's VLAN. Harness 47/47; the rename path and the stranded-link
check each proven able to fail.

Live remediation already applied to the dc0 region: subnet returned to
vlan 5002, the wrongly-created fabric deleted, fabric-1 renamed, space
re-bound. enp2s0 now reads fabric=vr1-dc0-provider-public with its static
intact.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HvCyrwvYTTcDYnRErfMsNf