docs: restore drill passed — S3 leg gate closed

18/18 instances replicated, restic seed complete and restore-tested
(tree identical to live; dump loads into a scratch MariaDB, 12/12
tables). Remaining ks2 gates are the nuc leg after FTTH.

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

ks2/plan.md

@@ -75,8 +75,10 @@ when nuc takes over.
 ## Release gates — ks2 can be dropped only when
 
 - [x] biwiki + spot consciously abandoned (2026-08-22)
-- [ ] local leg cron running ≥ a few days, all instances present
+- [x] local leg cron running since 2026-08-22, **18/18 instances**
+      replicated (verified 2026-08-28)
 - [ ] nuc leg fully seeded **and** one instance test-restored
-- [ ] restic S3 data/DB backups running daily **and** one DB + one
-      file tree test-restored
+- [x] restic S3 backups live (05:00) **and** restore drill passed
+      2026-08-28: tree restored byte-identical to live, dump restored
+      and loaded into a scratch MariaDB (12/12 tables)
 - [ ] ks4 crons pointing at ks2 disabled