Operator direction: "Proceed with 1 and 2". Item 2 (the repo tool for the MAAS half) is
delivered. Item 1 (the held ULA subnet) is NOT executed, and the tool is why.

THE TOOL'S FIRST LIVE RUN CAUGHT A DEFECT IN THE BY-HAND CHECK USED AN HOUR EARLIER, and
that is the more important finding here. It reported `interface links: subtle-grouse:enp1s0`
on subnet 2. My by-hand check had reported ZERO links for all five subnets, because the
subnet id was interpolated as sid="'$id'" -- the comparison ran against "'2'" and could
NEVER match. A checker that could not fail, written in the same session that landed exactly
that rule into script-authoring.md.

CONSEQUENCE: the earlier claim that the four deletes were "proven safe twice" was HALF
FALSE. The allocation count was sound; the link half was inert, so link status was UNKNOWN
at the time of those deletions.

THE OUTCOME WAS SAFE ANYWAY, MEASURED NOT ASSUMED: all nine role nodes read v4=6 v6=6, so
every v6 link they carry is GUA and the four deleted ULA subnets genuinely held none.
enp2s0 unlinked on all nine is EXPECTED (provider-public carries no L3 link; the static
lands on br-ex, D-133/D-100). subtle-grouse (the controller, Deployed) reads v4=2 v6=1, its
single v6 link being the ULA ::5 -- independently confirming the hold was correct. Right
outcome, unsound verification; recorded as two separate facts.

The mode lives in dc-plane-ipam.sh rather than a new script because dc-region-topology.sh's
header already assigns v6 plane subnets to it. It refuses on an allocation OR an interface
link, NAMES the holder, deletes one at a time (never looped, hard rule 3), and READS BACK
that the row is gone -- R6 proves that assertion has teeth by faking a delete that returns
success and leaves the row.

Harness 25 -> 32 (R1-R7), delta checked. R4 is the case that matters: an interface link
with NO allocation still refuses -- the exact blind spot the broken by-hand check had.

ITEM 1 NOT EXECUTED: retire-v6-ula REFUSES on fd50:840e:74e2:220::/64, naming ::5
(juju-vr1-dc0), ::6 (MAAS) and the link subtle-grouse:enp1s0. Deleting it needs the juju
controller's and region's v6 re-homed to GUA first -- re-addressing the DEPLOY CLIENT
immediately before the deploy, and this project has already lost three bootstrap attempts
to under-carved controller networking. Not covered by an approval given about four empty
subnets, and NOT deploy-blocking: an extra ULA subnet in MAAS harms nothing.

Gates: gauntlet ALL GREEN (98); repo-lint 0 fail; dc-plane-ipam 32/32.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HvCyrwvYTTcDYnRErfMsNf