Phase A (record amendments) + Phase B (scripts/dc-dc-whole-host-budget.py + harness) of the
Stage-3 adversarial-review sweep, plus the R-3 storage-04 addition (Model A layout now
3+2+4 = 9 nodes/DC). This commit is the R-3-COMPLIANT Model A state and becomes the re-cut
`model-a-fallback` anchor (the prior tag at 87a7a8a was R-3-stale -- 3 storage -- flagged by
the Model B design cross-check). NO cloud mutation; nothing applied.

- design-decisions.md: D-103/D-107/D-114/D-115/D-121/D-122/D-123/D-124 amendments (rulings R-1..R-4).
- scripts/dc-dc-whole-host-budget.py + tests/ (13/13): replaces the lost optc-calc.py (R3-F06).
- opentofu/main.tf: locals.vr1_dc0_nodes += storage-04 (R-3); tofu validate Success.
- security-ledger SEC-011 closed; session-ledger rulings + sweep progress; model-a-fallback plan.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ck6xh3jWQi5b3Su8Dx1LEH