Phase 0 delivery cleanup: session changelog with reverts, and a mis-filed finding corrected ...

Three gaps in the Phase 0 delivery, plus one new measured finding.

1. SESSION CHANGELOG ADDED (GA-R2/D1) -- docs/changelog-20260727-stage5-phase0.md.
   It was missing, and it is the only revert surface: no logged window was
   opened for this session, so the changelog + capture are the entire
   as-executed record of five live mutations (two branch deletions on origin,
   two on voffice1, a 68-package install on the region host). Each item now
   carries WHAT / WHY / HOW TO REVERT with the pre-state hashes recorded
   (39e8988, 61c416e, 57836b1) and the apt purge scoped with a caution that
   68 packages were pulled and some are shared.

2. CURRENT-STATE section 7 no longer carries two rows for one component. The
   prior "ABSENT ON BOTH HOSTS" state is folded into the single pin row as
   history, following the Juju row's in-row supersession precedent. A pin
   table asserting both presence and absence of the same client is the same
   stale-surface class the audit close-out sweep found the audit itself
   creating.

3. A FINDING I MIS-FILED IS CORRECTED BY MEASUREMENT. P4's
   "metal-admin gateway=none (want 10.12.8.1)" was dismissed as covered by
   readiness item 3.7. It is not -- 3.7 is specifically the VID-103 /
   br-internal assertions. Measured from the dc0 rack: 10.12.8.1 answers 0/2
   pings with an INCOMPLETE ARP entry (never resolved -- nothing holds it),
   against a control ping to the edge at 10.12.4.1 at 0% loss. So MAAS is
   right to carry no gateway and lib-net.sh:37's expectation is the defect, a
   VR0 inheritance; the D-134 carve ruled .1 gateways for the PROVIDER subnets
   only. Logged as P0-5, not fixed (hard rule 1). The dc1 arm (lib-net.sh:149)
   carries the same shape at 10.12.68.1.

Also queued for one GA-R5 exchange, no D-number assigned: which host is
authoritative for the gates. R10 (preflight on voffice1) and R15(3) (preflight
stops failing open) executed together make preflight-on-voffice1 permanently
unpassable given P0-2, and R15(2)'s manifest does not reach P0-1 -- so the R15
execution scope needs this answered first.

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