Add DC-DC deployment workflow overview + audited tooling gap register ...

Followable stage-by-stage checklist for the VR1 buildout (Stage 0 decision
ratification through Stage 7 Designate/COS/CAPI), cross-referenced to
docs/dc-dc-buildout-design.md and D-100..D-110. Includes an 11-item tooling
gap register audited directly against the repo (scripts/, tests/, netbox/,
runbooks/) rather than inferred from the design doc -- notably that
lib-net.sh/lib-hosts.sh are not actually DC-agnostic yet (single-deployment
hardcoded literals), which the Stage 5 reuse claim depends on, and that
OpenTofu has zero files in the repo today.

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