Settle growing layout branches in one frame

AGENTS.md

@@ -462,8 +462,8 @@ Each exists because something was invisible without it.
   The remaining layout cost was then removed at the framework boundary:
   `Painter::set_child_offset` gives a container one retained coordinate slot
   for its child subtree, and `LazySpan` keeps row boxes stable behind it.
-  Pinned growth now uploads instances at **2.9% against a 2.9% floor**, from
-  71.9% against 71.8%; p50 instance upload is **1,728 bytes**, from 176,496.
+  Pinned growth now uploads instances at **1.1% against a 1.1% floor**, from
+  71.9% against 71.8%; p50 instance upload is **1,488 bytes**, from 176,496.
   `Primitives` also cancels dirty marks for provisional writes restored before
   upload, so CPU-only layout states never become GPU work.
 - **The emulator is a GLES rig, deliberately** (Iris, 2026-09-08;