Tool-call cards and grouping, with the state a result never arrived in

P1b (docs/RUST.md). `transcript-ui/src/tool.rs` draws a card per tool
call and a group per run: collapsed, a card is its name and the one-line
summary `parse_tool_input` derives; open, it is the description, the
input (highlighted, on the verbatim surface) and the output, capped with
a "Show all N lines". A run is one surface with a heading and a chevron
bar at its foot, so it closes from either end.

Three things worth knowing.

**A collapsed card lays out its summary line and nothing else.** The
fixture's tool outputs are tens of kilobytes and a collapsed card never
builds a widget for one -- `collapsed_cards_shape_only_their_summary_
lines` opens a three-card group over 88 kB of output each and asserts the
text-shape count equals the same group's over three bytes (17 either
way; 17 against 20 when the discipline is deliberately broken, so the
test is real).

**A result arriving replaces one card.** `ToolRow::apply_calls` is the
group's half of `RowBlocks::apply_delta`'s rule, and `build_row` now
hands back one `TailRow` -- blocks for a message, cards for a run --
rather than two mechanisms chosen at each call site.

**Every tap is a tap**: `GestureOutcome::Tapped` out of the `DragArbiter`
`Selection` already owns, so a drag that started on a card scrolls the
transcript instead of opening it.

Three defects found by looking at the render, all recorded with their
repro in docs/IRIS_TODO.md: a `Span` of padded children inside another
`Span` places them a slot out of step (worked around by building the
group as one span, which costs the 4dp inset); `scrollable_on(Axis::X)`
on a non-editable text draws nothing, so a card's command is clipped
rather than pannable; and `NotoSans-Regular` has no U+25B8/25BE/25B4 at
all, so the expander mark is set in the monospace face.

Screenshots: docs/bench/p1b-2026-09-06/.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/IRIS_TODO.md

@@ -639,6 +639,49 @@ agent ticks it here with the evidence.
   it is its own item, most likely the report pane not masking or not
   claiming its region.
 
+## Found by P1b (2026-09-06), all with a headless repro
+
+Each was found by looking at `iris/run-headless.sh transcript -- -p
+transcript-ui` rather than at a diff, and each is worked around in
+`transcript-ui/src/tool.rs` rather than fixed here. docs/RUST.md's P1b box
+has the fuller account.
+
+- [ ] **A `Span` of `Pad`ded children inside another `Span` places those
+  children a slot out of step.** Each child drew its content one sibling's
+  height below its own box. Repro: `IRIS_TOOLS_EXPANDED=1
+  iris/run-headless.sh transcript --shot /tmp/x.png -- -p transcript-ui`
+  with `tool.rs`'s group built as `Span(DOWN)[header, Pad(Span(DOWN)
+  [cards]), bar]` instead of the single `Span` it uses now. Bisected:
+  removing the inner `Span` fixes it, and so does removing the children's
+  own `Pad`; the background `Stack`, the `Sized` wrappers and the
+  `WidgetPtr` per child make no difference. **Not** the `mov`-vs-
+  `reposition` fault f5b8893 fixed -- it survives that commit. The
+  workaround costs the group the 4dp inset its Compose counterpart holds
+  its cards off the edge by, so this is worth fixing.
+- [ ] **`scrollable_on(Axis::X)` on a non-editable `Text` draws nothing.**
+  The panel is drawn and the text inside it is not. A markdown fence does
+  the same to a `TextEdit` and is fine, so it is the widget kind rather
+  than the chain. `tool.rs`'s `raw_block` is `masked()` only until this is
+  fixed, which means a long command is clipped rather than pannable.
+- [ ] **No overflow ellipsis.** `TextAttrs` can wrap or not wrap; there is
+  no "one line, ellipsised" the way `maxLines = 1` + `TextOverflow.
+  Ellipsis` gives Compose. A tool card's summary is clipped instead, so
+  nothing on screen says it was cut. Whichever end is cut has to be a
+  choice when this lands: a path is identified by its tail, a command by
+  its head.
+- [ ] **A drawn chevron.** `Chevron.kt` draws its own strokes precisely
+  because a chevron from a font is a glyph a system font may not have --
+  and the bundled `NotoSans-Regular.ttf` indeed has no U+25B8/25BE/25B4,
+  while `NotoSansMono-Regular.ttf` does. `tool.rs` sets the mark in the
+  monospace face as a result. A real fix needs a line/path primitive;
+  iris has rects, text and textures only.
+- [ ] **A tool card's text is not selectable.** `Selection` is keyed
+  `(RowKey, block index)` and a card has no markdown blocks, so nothing in
+  a card registers. Compose's `SelectionContainer` covers tool output,
+  which is the text people most want to copy. Needs a key for "the nth
+  text of this row" that a card can mint without colliding with a
+  message's blocks.
+
 ## Build (for the port)
 
 Widgets `RUST.md`'s "The port, in order (decided 2026-09-05)" needs and