state: name the commit that survived the fold

Folding the 24 `state:` commits into the code they described gave every later
commit a new hash, so the verified-against line named 8a2ef08 — a commit only
the backup refs still hold. It is 8900aab in this history. Content unchanged;
the old sha resolved only because backup/pre-fold and origin/main still exist,
which is exactly the kind of advisory that would rot into a lie.

docs/state.md

@@ -1,6 +1,6 @@
 # State
 
-**Verified against:** `8a2ef08` on 2026-07-30 — update this line every change.
+**Verified against:** `8900aab` on 2026-07-30 — update this line every change.
 If this file disagrees with the code, the code is right and this file is a bug.
 
 ## Inventory