Say on_axis in the docs, and point the handoff at the tip

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/HANDOFF.md

@@ -6,7 +6,7 @@ found is in `docs/LAYOUT_LOG.md`.
 
 ## The Iris layout repair is submitted
 
-**Iris PR #19** (`layout/one-ask`) replaces closed #18. The tip is `2807a92`,
+**Iris PR #19** (`layout/one-ask`) replaces closed #18. The tip is `4d42f1c`,
 and past the reviewed `cadfba0` it is three rounds:
 
 - **The repair.** `add6774` fixes collapsed-share placement, retained mask
@@ -22,7 +22,7 @@ and past the reviewed `cadfba0` it is three rounds:
   with Bryan on 2026-09-19. A description is built by chaining off the value
   that says it (`UiSpan::shifted_desc`, `Len::as_desc`), never by a
   constructor naming the type; `on` is reserved for events, so the lift is
-  `PlaceDescAxis::axis`. Arithmetic that needed a comment became a name:
+  `PlaceDescAxis::on_axis`. Arithmetic that needed a comment became a name:
   `UiSpan::place`, `LayoutLen::without_leftover`/`is_px`/`is_only_leftover`/
   `declared`, `Holds::covers`. `LayoutHolds` became `AxisHolds` on `x`/`y`,
   every pair got `Index<Axis>` through `impl_axis_index!`, and the bare

docs/LAYOUT.md

@@ -371,7 +371,7 @@ wrong with nothing failing.
 `PlaceDesc` is the pair, with `x` and `y` fields and the `Index<Axis>` and
 `from_axis` of every other pair here, so the joint work — resolving a
 region, reading the fill flags — is written once rather than per axis.
-`PlaceDescAxis::axis(axis)` goes the other way, lifting one axis into a pair
+`PlaceDescAxis::on_axis(axis)` goes the other way, lifting one axis into a pair
 with the whole box across it.
 
 **Every pair here is a struct of two per-axis values, read with `[axis]`.**