iris: a widget's move slot has one owner -- move_applied + repositioned

`mov` accumulates a delta onto the slot and `reposition` overwrote it, and
both legitimately land on one widget in one frame: `List::place`'s
Bottom-known branch offers a row a same-size box that has moved (`mov`),
then corrects the placement inside it when the row's cached height no
longer matches what the row reports (`reposition`). That is what a wrapped
transcript row hit, and what the `move_applied == ZERO` debug assert was
standing in for -- an assert against a case that happens is not a
guarantee, it is a crash.

The slot means `move_applied + repositioned` now, both halves recorded on
`ActiveData`, so `reposition` adds the move rather than dropping it and
stays idempotent. The assert it replaces is a `debug_assert_eq!` that the
slot still holds that sum on entry -- i.e. that nothing but those two ever
wrote it.

Test: `a_widget_moved_by_its_parent_and_then_placed_inside_it_lands_at_the_placement`,
which draws the child at the offered position (-100px) rather than the
placement (100px) without the fix. Verified against the `.wrap(true)`
repro from docs/IRIS_TODO.md (draws correctly, no panic) and an emulator
bench run with assertions live.

docs/IRIS_TODO.md

@@ -591,17 +591,23 @@ agent ticks it here with the evidence.
   that. Fixed in `iris/src/widget/rect.rs`; the reason is written at the
   definition. Suspect the same cause for anything else tinted with a
   background rect.
-- [ ] **A wrapped transcript row trips `reposition`'s debug assert.**
-  *"widget ... is both moved by its parent's own layout (`mov`) and
-  repositioned within it"*, raised from `List::place`. Repro: change
-  `.wrap(!verbatim)` to `.wrap(true)` in `transcript-ui/src/row.rs`'s
-  `build_block` and run `iris/run-headless.sh transcript --shot
-  /tmp/x.png -- -p transcript-ui`. Survives the `Rect` fix above and is
-  not specific to any block kind -- it appears once the row is tall
-  enough. The shipping configuration does not reach it (verbatim blocks
-  do not wrap) and the Android bench runs clean with assertions live,
-  but it is a real disagreement about who owns a widget's move slot and
-  should be settled before more of P1 leans on `List`.
+- [x] **A wrapped transcript row tripped `reposition`'s debug assert.**
+  Settled 2026-09-06 by giving the move slot one owner instead of two.
+  `mov` accumulates a delta on it, `reposition` overwrote it, and both
+  legitimately land on one widget in one frame: `List::place`'s
+  Bottom-known branch offers a row a same-size box that has *moved*
+  (`mov`), then corrects the placement inside it when the row's cached
+  height no longer matches what the row reports (`reposition`). The
+  slot now always means `move_applied + repositioned`
+  (`ActiveData::repositioned`, `iris/core/src/ui/render_state.rs`), so
+  `reposition` adds the move rather than dropping it -- the assert is
+  gone and the arithmetic is right. Test:
+  `a_widget_moved_by_its_parent_and_then_placed_inside_it_lands_at_the_placement`
+  in `layout_tests.rs`, which lands the child at the *offered* position
+  (-100px) instead of the placement (100px) without the fix, and a
+  `debug_assert_eq!` in `reposition` that nothing but those two ever
+  writes the slot. Verified with the `.wrap(true)` repro (draws, no
+  panic) and an emulator bench run with assertions live.
 - [ ] **Desktop colours are washed out: the winit surface is sRGB and
   the shader writes the palette's bytes as linear.** Mocha Crust
   (17,17,27) is drawn as (73,73,91), measured off
@@ -624,6 +630,15 @@ agent ticks it here with the evidence.
   backend too -- `./run-headless.sh transcript --shot /tmp/x.png -- -p
   transcript-ui --features iris/force-gles`.
 
+- [ ] **The bench report pane draws over the transcript rows instead of
+  replacing them.** Visible on the emulator for the first time now that
+  glyphs render there (`/tmp/emu-final.png`, 2026-09-06): after a bench
+  run the report's lines and the transcript's occupy the same rows in the
+  top third of the screen, both legible, neither on top. Pre-existing --
+  the same overlap is in a screenshot taken before the move-slot fix -- so
+  it is its own item, most likely the report pane not masking or not
+  claiming its region.
+
 ## Build (for the port)
 
 Widgets `RUST.md`'s "The port, in order (decided 2026-09-05)" needs and