docs: close the three untested items — all three are now measured

D-2 forward upgrade and B-4 role propagation were filled earlier. D-4 forced
renewal was the third, and it needed a person at the keyboard because the
host asks for a sudo password.

It turned out to hold the largest finding of the three: the renewal
succeeded and went unserved for 36 minutes 39 seconds, because nothing in
the setup reloads nginx — no ExecStartPost, three empty hook directories,
no nginx plugin. And the half of the plan's question that was still an
expectation is now a measurement: the reload is graceful, 8856 connections
with zero failures and an in-flight request surviving intact.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/experiment-index.md

@@ -27,7 +27,7 @@
 | **D-2** | 버전 업그레이드 | `...d2-version-upgrade` | **이미지를 되돌려도 스키마는 안 돌아온다** |
 | **D-3** | 비밀 관리 | `...d3-secret-management` | **RBAC 만 실제로 감춘다** |
 | **D-4** | 인증서 갱신 | `...d4-certificate-renewal` | **갱신은 됐는데 36분 39초 반영 안 됨** (훅 3경로 전부 비었음). reload 자체는 **무중단**(8856건 0실패) |
-| **후속** | 미측정 항목 채우기 | `...followup-untested-items` | 정방향 업그레이드 무중단 · **롤백 불가는 조건부였다** · role 변경은 요청으로 반영 안 됨 |
+| **후속** | 미측정 3항목 채우기 | `...followup-untested-items` | **셋 다 완료.** 정방향 업그레이드 무중단 · **롤백 불가는 조건부였다** · role 변경은 요청으로 반영 안 됨 · **D-4 갱신 36분 39초 미반영** |
 
 ## 시각 자료