fix(#2491): finish todos/done -> todos/completed rename (14 stale refs) + guard (#2626)

* test(#2491): add todos/done rename under-sweep guard

* fix(#2491): finish todos/done -> todos/completed rename (14 stale refs)

* chore(#2491): backfill changeset pr to 2626

* test(#2491): fix lint-legacy-dir-name + allow-test-rule-refs (split legacy token, add issue ref)

docs/ko-KR/ARCHITECTURE.md

@@ -538,7 +538,7 @@ UI-SPEC.md (단계별) ───────────────────
 │       └── SUMMARY.md
 ├── todos/
 │   ├── pending/            # 캡처된 아이디어
-│   └── done/               # 완료된 할 일
+│   └── completed/          # 완료된 할 일
 ├── threads/               # 영구 컨텍스트 스레드 (/gsd-thread에서)
 ├── seeds/                 # 미래 지향적 아이디어 (/gsd-capture --seed에서)
 ├── debug/                  # 활성 디버그 세션

docs/ko-KR/USER-GUIDE.md

@@ -853,7 +853,7 @@ All subagent/executor commits MUST use `--no-verify`.
   reports/                # Session reports (from /gsd-pause-work --report)
   todos/
     pending/              # Captured ideas awaiting work
-    done/                 # Completed todos
+    completed/             # Completed todos
   debug/                  # Active debug sessions
     resolved/             # Archived debug sessions
   spikes/                 # Feasibility experiments (from /gsd-spike)