D-126 base-leg oneshot (site-baseleg.sh) + D-128 operating model; post-restart sweep ...

vcloud post-restart health sweep all-green (host on 6.8.0-136, patch+reboot done;
libvirt/pools/autostart clean; Office1 stack self-recovered end-to-end). Sweep
surfaced a recurring break: office1-local is an ISOLATED libvirt net, so the host's
base L3 leg (10.10.0.10/24 on the bridge + compose route 10.10.1.0/24 via 10.10.0.20)
lives nowhere in the XML and drops on every reboot -- the un-persisted foundation
D-126 assumed but never owned.

- NEW scripts/site-baseleg.sh + tests/site-baseleg/ (24/24): root Type=oneshot unit,
  After=libvirtd (+virtnetworkd for modular hosts; ordering MEASURED here = monolithic
  libvirtd), re-adds the leg at boot. Bridge DISCOVERED from the stable net name (never
  a baked virbrN, PATTERN-1); apply idempotent + root-guarded; check = session-verify.
  INSTALLED + enabled this session; boot-race UNPROVEN until an actual reboot.
- docs/design-decisions.md: D-126 amendment (base-leg durability) + NEW D-128 (operating
  model -- Claude on the vcloud jumphost; Plane-1 substrate on vcloud / Plane-2 executes
  on voffice1; workstation tailnet is the human path; D-107 untouched).
- Skill invariant + routing row (SKILL.md), Cross-cutting bullet (dc-dc-deployment-workflow.md),
  session-ledger + changelog.

Gauntlet ALL GREEN (67 harnesses), repo-lint 0-fail. Nothing merged to main (stage-close).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QMKdXCquMnh1jKH2sWXPMg