docs: mark GeoEdge.discord as design-branch-only, not on dev

The line references were correct but silently implied the code was on dev.
It is on design/correspondence-and-censorship (a8845e1). On dev,
co_registration is still at engram_geometry.h:79 with its original comment
and still unread by anything.

AGENTS.md

@@ -96,9 +96,10 @@ manifest materializes a property as a stored artifact and enumerates instances o
 something that has six. A sweep over regions is a supervisor — nothing in a mind
 scans its neighbourhoods to find what is surprising; the surprise captures
 attention. The nucleation site is per-edge:
-`discord = z(semantic proximity) − z(association strength)`
-(`lang/runtime/engram_geometry.h:43–47`), and `|discord|` *is* the nucleation
-strength — no threshold to compare it against. The region-level aggregate
+`discord = z(semantic proximity) − z(association strength)`, and `|discord|` *is*
+the nucleation strength — no threshold to compare it against. **Not on `dev` yet:**
+`GeoEdge.discord` is on branch `design/correspondence-and-censorship`
+(`a8845e1`), at `lang/runtime/engram_geometry.h:43–47`. The region-level aggregate
 `GeoDescriptor.co_registration` is **deprecated**: it averaged a per-edge property
 into one scalar, so opposing sites cancelled (measured: 375 reified
 neighbourhoods, 340 positive, **31 at zero**, 4 negative). It survives only