DOCFIX-144: opentofu/modules/node-vm + fix real syntax bug in DOCFIX-142 ...

Built the D-103 node-VM pattern (blank disk, PXE-boot, MAAS-managed) for
Stage 3 -- this time from the provider's own real example .tf files
(examples/domain_with_network.tf, examples/alpine_cloudinit.tf), not
doc-summarization alone, since that confidence gap is exactly why the domain
module was deferred last time.

That surfaced a real bug in the already-pushed dc-planes/mesh-link/
dc-storage-pool modules (14d7382): they used classic HCL block syntax
(domain { ... }) where this provider's current schema needs attribute-style
objects (domain = { ... }) -- confirmed once real examples showed the actual
convention. All three fixed; opentofu/README.md's schema notes now state this
as a provider-wide assumption for any field not personally confirmed
otherwise.

One inference flagged, not presented as fact: the per-device boot-order
attribute's exact internal shape ({ order = N }) -- the field's existence is
confirmed, its shape is not. Not instantiated in root main.tf: node
count/sizing is a pending Phase-0 decision, not invented here. Still
deferred: the cloud-init/base-image VM pattern (Office1 services + OPNsense),
DC2 planes, netem application.

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