DOCFIX-164: D-101 IPv6 family-matrix overlay, researched against real charm source (gap #13) ...

overlays/dc-dc-ipv6-family-matrix.yaml + docs/dc-dc-ipv6-charm-research.md.
Fetched real charm config/source (not memory): prefer-ipv6 is a real,
shared charms.openstack option, confirmed genuinely additive dual-stack
(not either/or) via charm-nova-cloud-controller's actual "Dual Stack VIPs"
commit; ceph-mon's own prefer-ipv6 is a straight switch, correct for the
ULA-only planes; OVN has no such option at all (confirmed by reading its
full config.yaml) and needs no overlay entry; vault's cert code has no
v4/v6 distinction, confirming D-109's SAN requirement is code-supported.

Found and deliberately did not paper over a real open risk: Octavia's
lb-mgmt-net has two real, still-referenced upstream IPv6 bug reports.
Excluded from the overlay pending an explicit operator decision.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QrcJx8TUar7pYAvpGJw57A

DOCFIX-154/155/156: Stage 2/3/5 runbooks -- Office1 standup, DC substrate, per-DC bundle ...

Three DC-DC runbooks authored in parallel this evening:
- Stage 2 (Office1 headend standup): MAAS-region/NetBox/GitBucket/Tailscale,
  each VM-creation step forking an explicit OpenTofu-blocked vs manual-debt
  path rather than picking one silently. Flags a real gap: no Office1-local
  network is modeled in opentofu/.
- Stage 3 (OpenTofu builds each DC substrate): DC1-first, DC2 hard-gated on
  NetBox literals. Walks every open decision (node sizing, MAAS zone/pool,
  config.xml tokens, netem params) and stops rather than inventing values.
- Stage 5 (Juju controller + bundle, per DC): describes adapting the
  existing phase-01..08 loop to run twice, not duplicating it. Mandates the
  $DC selector convention (DOCFIX-151) before every adapted command block.
  Surfaces the undesigned IPv6 family-matrix overlay as blocking work.

All three: not yet executed (prep-only session, no live infrastructure
reachable tonight); repo-lint 0 fail/1 documented warn.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QrcJx8TUar7pYAvpGJw57A