Merge pull request 'Design 47's B0 says its one new seat verb is delivered first, alone (issue 1921)' (#525) from feat/b0-checking-program into main

03-DESIGN/01-to-be/47-delivery-from-commit-to-delivered.md

@@ -2466,7 +2466,13 @@ order inside one milestone, for this one case (ADR 0644).
   trunk's manifest validator, built from the trunk (ADR 0633 §6).
 - **The running checker checks it.** B0 changes no seat definition and adds no manifest field, so the running checker
   reads every manifest of it; for B0's own group, what the running checker cannot run is still composed from its
-  manifest and named in the verdict, as ADR 0603 §10 and ADR 0614 §7 have it until milestone G (ADR 0656 §5).
+  manifest and named in the verdict, as ADR 0603 §10 and ADR 0614 §7 have it until milestone G (ADR 0656 §5). B0 does
+  add one verb to the seat list compiled into mesh-sdk, the checker seat's `input`, which the running indexer did not
+  know: B0's first check refused mesh-build-go (which invokes it) and mesh-delivery-checker (which serves it), because the
+  check's composition took the running indexer's verdict on the change's own manifests over the check's own manifest
+  validator, which accepted them. So that verb alone is delivered first, as a release of one mesh-sdk change, which
+  rebuilds the indexer (ADR 0573 §3); B0 is checked after it (the operator, 2026-11-07). A check that honours its own
+  validator on the manifests a change brings, in every composition, is milestone G's.
 
 B0's own choices, each checked by the rows of *How it is checked* below: