1c/C6: operator override — keep FINAL W5 throwaway (promote -> cc-nix-test); defer teardown

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

DECISIONS.md

@@ -210,4 +210,10 @@ Architecture decisions and dead-ends. One line of rationale each. (§0, §8)
 - **Cert into git:** wildcard cert+key become sops secrets in `cc-ci-secrets`, decrypted at
   activation back to `/var/lib/ci-certs/live/{fullchain.pem,privkey.pem}` via
   `sops.secrets.<name>.path`; proxy.nix keeps reading that path (now sops-sourced, not operator-drop).
-- **cc-nix-test final sizing:** TBD in W6 (keep 4 GB / restore 6 GB / promote rebuilt VM).
+- **cc-nix-test final sizing (C6) — SETTLED by operator 2026-05-27: PROMOTE the rebuilt VM.** The
+  freshly-rebuilt reproducible VM (the FINAL W5/C4-C5 clean-room throwaway) becomes the canonical
+  cc-nix-test; the operator will repurpose it for a live real-traffic test through the public gateway.
+- **C6 teardown OVERRIDE (operator, 2026-05-27):** do NOT destroy the FINAL throwaway VM after
+  W5/C4-C5 PASSes — keep it RUNNING; defer its C6 teardown until the operator explicitly says
+  otherwise. This overrides the plan §5/§6 "destroy the throwaway" for that one VM only. All other
+  cleanup proceeds normally (the Builder's first throwaway was already destroyed; RAM accounting holds).