Record the logic sweep and point the handoff at 6c84b6f

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 `4d42f1c`,
+**Iris PR #19** (`layout/one-ask`) replaces closed #18. The tip is `6c84b6f`,
 and past the reviewed `cadfba0` it is three rounds:
 
 - **The repair.** `add6774` fixes collapsed-share placement, retained mask
@@ -27,6 +27,12 @@ and past the reviewed `cadfba0` it is three rounds:
   `declared`, `Holds::covers`. `LayoutHolds` became `AxisHolds` on `x`/`y`,
   every pair got `Index<Axis>` through `impl_axis_index!`, and the bare
   `[Option<LayoutLen>; 2]` became `Declared` of `Option<Len>`.
+- **A sweep over the logic the clearer methods exposed**, `8d2b7a5` and
+  `6c84b6f`. A `Span` carried `start` as a third accumulator when it was
+  always `fixed` and `taken` read together, so both ends of a slot are now
+  read where they are used. A `Scroll`'s draw writes `amt` and `snap_end`,
+  so warm and cold agree only because re-clamping is idempotent; the seed
+  scans build scrolls and never scroll one, so a test now pins it.
 
 The core design remains sound. Round-to-nearest is still unchanged.