Record the refcount removal beside the sweep that raised it

docs/LAYOUT_LOG.md

@@ -10,7 +10,7 @@ the current plan is in `docs/HANDOFF.md`.
 
 Over the whole branch again, aimed first at what allocates -- `Vec`s, `Arc`s,
 capacity dropped and re-grown -- and then at whatever else the reading turned
-up. Eight findings.
+up. Nine findings.
 
 - **A container's draw was quadratic in its children.** Every per-child step
   in one draw asked "have I done this one already?" by searching a list:
@@ -116,7 +116,24 @@ up. Eight findings.
   does not clip it, because masking is a capability a caller opts into by
   putting a `Masked` around it. The code is right; the reason was not.
 
-Five things the sweep **looked at and left**:
+- **`StrongWidget` carried a `RefCounter(Arc<AtomicU32>)` it could never
+  use.** It deliberately has no `Clone`, so the count never rose above zero,
+  `RefCounter::drop` always answered true, and `StrongWidget::refs` had no
+  caller -- while every widget made paid a heap allocation and every one
+  created or dropped paid two atomic read-modify-writes. Removed: the handle is
+  the id, the sender and the type, and `Drop` sends. It is 32 bytes rather than
+  40, and 40 rather than 48 for a `dyn` one. Raised as something to leave for
+  the pre-gate pass, `handle.rs` being outside #19, and Bryan asked for it here
+  (2026-09-21): not being `Clone` is what makes one handle the only one, which
+  is the same fact the child note above rests on.
+
+  `RefCounter` stays for `TextureHandle`, which does clone -- several widgets
+  showing one picture share its slot -- and is down to what that needs:
+  `quiet_clone` and `refs` had no callers at all, and `new` was `Default` spelt
+  out, so the default is derived now and says in one line that zero means one
+  handle.
+
+Four things the sweep **looked at and left**:
 
 - **Text allocates about six times per re-broken paragraph per frame**, and it
   is not worth removing. One is the whole text copied into the placement store
@@ -129,13 +146,6 @@ Five things the sweep **looked at and left**:
   is **0.07%**. The machinery is two pools and a changed `place` signature for
   that, so the count is recorded here instead. Allocation count is not the
   same quantity as cost, and this is where the two part.
-- **`StrongWidget` carries a `RefCounter(Arc<AtomicU32>)` it can never use.**
-  `StrongWidget` deliberately has no `Clone`, so the count never rises above
-  zero and `RefCounter::drop` always answers true -- but every widget still
-  allocates an `Arc`, and creating and dropping one is two atomic
-  read-modify-writes. `StrongWidget::refs` has no caller. `handle.rs` is
-  untouched by #19, so this belongs to the review of the code written before
-  the gate; recorded there.
 - **More for that same pass, all dead and all older than #19**:
   `Size::to_uivec2`, `Size::rel`, `Size::leftover`, `Len::to_uivec2`,
   `Vec2::with_x`, `Vec2::with_y`, `Vec2::ceil`, `Layers::iter_orderless_mut`.
@@ -151,6 +161,11 @@ Five things the sweep **looked at and left**:
   the duplication is bounded by what the caller wrote rather than by anything
   the arena does on its own.
 
+One more thing **looked at and left** in passing: `RefCounter` decrements with
+`Ordering::Release` and has no acquire on the last drop, which is the shape an
+`Arc` gets wrong when handles cross threads. Left because nothing here is
+threaded and the orderings are not this sweep's to guess at.
+
 Verified at the sweep's tip: format, workspace clippy under `-D warnings` with
 and without `layout-diagnostics`, **190** ordinary, **193** diagnostic and
 **189** release tests (188 and 191 before, with release failing), and the cold