DC-DC Stage 1 (dc-dc-phase0): first real execution + scaffold/tooling fixes ...

First end-to-end run of a DC-DC runbook against real infrastructure (vcloud host,
OpenTofu v1.12.3). Applied 13 libvirt objects (6 DC1 planes, dc1/office1/dc2
pools, office1-local, 3 mesh legs, all MTU 9000); prior VR0 nets torn down (wan
kept as a gap-#17 model); DC2 planes deferred (NetBox supernet), DC2 storage wired.

DOCFIX-178: scripts/prereqs/ idempotent workstation prereq installers + a
  Prerequisites section in the runbook + tests/prereqs/ (25/25). Runbooks must
  not assume prereq runtimes.
DOCFIX-179: OpenTofu scaffold first validation + apply. Per-module
  required_providers (child modules do NOT inherit provider SOURCE -> OpenTofu
  inferred nonexistent hashicorp/libvirt); tofu fmt -recursive; provider "maas"
  deferred to Stage 3 (kept a sensitive key out of Stage-1 plan/state);
  repo-lint now skips the .terraform/ provider cache; .terraform.lock.hcl added.
DOCFIX-180: dc-dc-phase0 runbook as-executed corrections folded in at phase
  close (two MTU domains, non-pristine-host handling, Step-9 13-resource plan,
  -input=false, Known-Gap resolved).

repo-lint 0 fail; prereqs harness 25/25; repo-lint harness 34/34.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

DOCFIX-147: opentofu/modules/maas-vm-host + modules/netem-link ...

Registers the vcloud host with MAAS as a virsh VM host, and applies tc netem
WAN-simulation parameters -- the two remaining unbuilt mechanisms from the
OpenTofu scope, researched before drafting per instruction.

maas-vm-host uses canonical/maas's maas_vm_host (register the chassis so
MAAS discovers already-existing VMs), deliberately not maas_vm_host_machine
(composes new VMs itself -- takes cores/memory/disks as inputs). Read both
schemas and cross-checked against D-103's explicit "MAAS does NOT compose
new ones" before picking one.

netem-link uses terraform_data (OpenTofu's own recommended replacement for
null_resource) with an SSH-wrapped local-exec provisioner -- confirmed
local-exec runs on the machine invoking tofu apply (Office1 per D-103), not
the vcloud host where the bridges live, so a bare local command would do
nothing useful.

Neither module instantiated: needs a real MAAS zone/pool, the vcloud host's
SSH target, and real netem parameters, none of which exist yet.

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