docs: scope window insertion to immediate successors

TRIAGE.md

@@ -101,12 +101,14 @@ Every issue you mint carries, in this order:
   During a standing release window, every mint also gets a binary membership
   call in the same tick. A non-member names the release issue as its blocker
   in its own Dependencies. A member is placed with three writes: the new issue
-  names its immediate member predecessors; every downstream member adds or
+  names its immediate member predecessors; every member whose immediate
-  re-points its dependency to the new issue, dropping any predecessor the new
+  predecessor the new issue becomes adds or re-points its dependency to the
-  issue now reaches (inserting X into A → B makes A → X → B, so B drops A);
+  new issue, dropping any predecessor the new issue now reaches (inserting X
-  and the release issue adds the new issue to its gate, recording membership
+  into A → B makes A → X → B, so B drops A); a member that must land after the
-  only. A member may have multiple successors. Collision and window edges are
+  new issue but already reaches it through another member declares nothing
-  independent, so write both when both apply (#292).
+  new; and the release issue adds the new issue to its gate, recording
+  membership only. Collision and window edges are independent, so write both
+  when both apply (#292).
 - **Labels**: type (`bug`/`enhancement`/`documentation`), `scope:*`, and
   exactly one of `ready` / `blocked` (see [LABELS.md](LABELS.md)).