Found by a repo-wide grep, not by any gate. Two faults, one cause -- I
measured and gated the population the QUESTION named (the 13 VIP charms)
rather than the population the INVARIANT covers (every application juju
validates).

(1) PREFER_IPV6_CHARMS was WRONG. Re-measured across ALL 33 charms in
bundle.yaml: TWELVE declare the option, not seven. The five missing are
ceph-mon 491, ceph-osd 953 (squid/stable), nova-compute 894, hacluster 166
(2.4/stable) and mysql-innodb-cluster 164 (8.0/stable).

(2) 9a was written INSIDE the VIP loop, so an application with no vip never
reached it -- and the repo ALREADY has that case:
overlays/dc-dc-ipv6-family-matrix.yaml sets prefer-ipv6 on ceph-mon, which
carries no VIP. That overlay is a LATER deploy step, so the miss would have
passed attempt 2 cleanly and surfaced at the step after, looking like a new
fault.

9a now runs over EVERY application, before the VIP loop; the VIP loop skips an
app 9a already flagged so the diagnosis is not doubled. ceph-mon's own in-file
claim of the option is now INDEPENDENTLY VERIFIED from the artifact rather
than taken from the comment.

Harness 48 -> 50/50. T47 (non-VIP app whose charm lacks the option FAILS) and
T48 (ceph-mon PASSES) both mutation-proven: re-scoping 9a back to the VIP loop
kills T47; dropping ceph-mon from the list kills T48.

Gauntlet ALL GREEN (93); repo-lint 0 fail.

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