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.md

@@ -8,6 +8,51 @@ capability that moved. Small and trivial changes do not go here.
 An entry gives the date, what changed, why, and a short before/after where
 it helps judge the change without the session that made it. Newest first.
 
+## 2026-09-06: tool cards, `ToolState`, and a screen that knows whether its session is working
+
+`transcript_ui::tool` is new: a card per tool call, a group per run
+(P1b). Three things in the public surface follow from it.
+
+**`client_core::transcript_fold::ToolState`** is what a card colours
+itself by -- `Running`, `Deciding`, `Succeeded`, `Failed`, `NoResult` --
+built by `ToolState::of(&item, session_working)`. The pair it exists for
+is `Succeeded` against `NoResult`: a call that finished having printed
+nothing and a call whose result never arrived both leave an empty
+`output`, and drawing them the same way states a verdict nobody reached.
+Only the session's own status separates them, which is why `of` takes it.
+
+**`event_model::Event::ToolEnd` gained `is_error`** (`#[serde(default)]`,
+so an older transcript still parses), and
+`client_core::transcript_fold::TranscriptItem::ToolRun` gained `failed`.
+Without them a result was everything a card knew and a broken call drew
+exactly as confidently as one that worked -- the missing state, not a
+wrong one. Every construction site of both had to gain a field; the value
+comes from the CLI's own `tool_result`, read in one place
+(`import::tool_result_is_error`) by both the live translator and the
+import replay.
+
+**`TranscriptScreen::set_session_working(rsc, bool)`** is new, and is the
+only thing that writes it. Before: a card with no result was drawn the
+same whether its turn was still going or had been interrupted. After:
+only the *newest* row can say "running", because every row behind it
+belongs to a turn that has ended, and changing the flag redraws that one
+row rather than the screen. `TranscriptScreen::expand_tail_tools(rsc,
+bool)` joins it, answering whether there was a tool run to act on -- a
+group's expanded appearance is otherwise unreachable from anything that
+cannot press the screen.
+
+**`transcript_ui::row::build_row` now returns a `TailRow`** rather than an
+`Option<RowBlocks>`: `Blocks` for a message (a delta costs the last
+markdown block) or `Tools` for a run (an arriving result costs one card).
+One mechanism for "what can this row change cheaply", asked of the row
+rather than decided again at each call site. It also takes the row's own
+`working` flag.
+
+Two smaller ones. `client_core::tool_summary::parse_tool_input` is
+`ToolInput.kt`'s subject/description/timeout/rest split, and
+`client_core::durations::format_millis` is `Durations.kt`'s -- both pure,
+both with the Kotlin's own tests ported.
+
 ## 2026-09-06: a tap is its own gesture outcome, and opening a URL is a backend capability
 
 Three related additions, all for following a markdown link.