docs: give the twelve experiments that had no architecture diagram one

An audit against the standard the series set — concepts, procedure,
commands, architecture diagram, evidence table, terminal output — found the
three new experiments met it while twelve of the original ones had no
diagram at all: A-0, A-1, A-3, A-4, A-5, A-6, A-8, B-0, B-2, B-7, C-2, D-2.

Each now has one drawn from what that experiment actually found, not filler:
A-0 shows sharing going through PostgreSQL rather than between the caches;
A-3 the gap between the 200 and the WAL flush, with both failed injections;
A-5 the three silent injection failures; A-6 the two places latency is
multiplied; B-0 the repository keyed by principal with no session id; B-2
the primary key that causes the overwrite; D-2 why the rolling update
stopped the accident halfway.

Also corrected the index's stale claim of 11 experiments without a
screenshot — it is 14, and the reason is recorded: those experiments were
measured from terminals, the database and logs, and the observability stack
does not scrape Redis, the BFF or PostgreSQL, so there is no console to
photograph.

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

docs/experiment-followup-untested-items.md

@@ -10,6 +10,18 @@
 
 ---
 
+## 구조
+
+이 문서는 세 실험의 후속이므로 각자의 구조도를 참조한다.
+
+| 항목 | 구조도 |
+|---|---|
+| D-2 정방향 업그레이드 | [`d2-version-upgrade.svg`](diagrams/d2-version-upgrade.svg) |
+| B-4 ③ role 반영 | [`b4-header-forgery.svg`](diagrams/b4-header-forgery.svg) |
+| D-4 강제 갱신 | [`d4-renewal-gap.svg`](diagrams/d4-renewal-gap.svg) · [`d4a-hook-timeline.svg`](diagrams/d4a-hook-timeline.svg) |
+
+---
+
 ## 0. 결론부터
 
 | 항목 | 결과 |