docs(agents): say who owns a campaign ledger

The dedupe passes kept trying to port single-owner experiment figures into
endpoint Eras tables. The law now states the test explicitly: two pages
carrying one figure is the defect; a figure with exactly one holder is fine
wherever it lives.

AGENTS.md

@@ -342,7 +342,11 @@ file is a defect: it is the next thing to go stale.
   serve script that consumes it, and in the endpoint page. Every other page
   cites it by link.
 - Technique pages (spec decode, KV math, offload budgets, PP bandwidth) stay
-  technique pages; they stop carrying per-endpoint throughput tables.
+  technique pages: they stop carrying a per-endpoint throughput table or a live
+  shape, but a campaign ledger that exists nowhere else is owned by the page that
+  measured it. The defect is two pages carrying one figure, not a number living on a
+  technique page — move a figure only when an endpoint page or an env header is its
+  home; otherwise leave it in place and name the era it measured.
 
 ## Model Config (harness)