RUST.md, IRIS.md, IRIS_TODO.md: record I5 -- transcript-ui built and

partial, the recommendation's numbers still missing

I5's own box: the seven "hard to get back" behaviours each shown or
given a sourced reason, the exact verification commands and results,
and what remains (Android integration, touch-drag-vs-selection
arbitration, row accessibility names, a tappable link, code-span chip,
selection's anchor-row shortcut, code-fence syntax highlighting) --
each also a dated IRIS_TODO.md item so it is not silently dropped.
Ticked [~] rather than [x]: the widget-tree half is built and tested,
the emulator half is not.

"Where things stand" and the Recommendation's item 3 updated in place
to say plainly that neither Masonry (E2) nor iris (I5) has produced a
render number yet, and why -- not a bad measurement, no measurement
obtainable yet on either side -- with the structural findings that do
exist (iris now does cross-row selection and per-span inline rich text,
neither of which exists in masonry/masonry_core/xilem today) recorded
as what currently favours iris absent a number.

IRIS.md gets SpanStyle's own entry: what changed, why, and the one
thing a future TextBuilderOutput impl must remember (both TextOutput
and TextEditOutput apply .spans() -- this box shipped the bug of
missing one of the pair once already).

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

IRIS.md

@@ -8,6 +8,47 @@ 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.
 
+## 2026-09-05: `SpanStyle`, per-range text styling (RUST.md's I5)
+
+A `TextBuffer` used to have exactly one style (`TextAttrs`: colour, size,
+family, ...) for its whole string, applied via `push_default` into parley's
+ranged builder. `SpanStyle` is a second, optional layer: a byte range plus
+whichever of colour/family/font size/bold/italic/underline it overrides,
+pushed with parley's own `push(property, range)` instead. Why: a transcript
+row's markdown (a heading, **bold**, `inline code`, a link) all inside one
+wrapped paragraph needs each to carry its own look while the paragraph
+still wraps and selects as a single buffer — the thing `masonry`'s
+`TextArea` cannot do (`StyleSet` is one style for the whole editor,
+`text_area.rs:43-44`'s `// TODO: RichTextInput`), and the reason this
+existed at all.
+
+```rust
+let (text, spans) = transcript_ui::markdown::render_markdown(src, 16.0);
+wtext(text)
+    .spans(spans)   // new: TextBuilder::spans, on both Text and TextEdit
+    .editable(EditMode::MultiLine)
+    .add(rsc);
+```
+
+Two things a widget author should know before reaching for it:
+
+- **Call `.spans()` before or after `.editable()`, both work** — the field
+  lives on `TextBuilder` itself, not either output type, and both
+  `TextOutput::run` and `TextEditOutput::run` apply it to the buffer via
+  `TextBuffer::set_spans`. **These two call sites are a pair**: adding a
+  third `TextBuilderOutput` impl without also calling `set_spans` there
+  reproduces the exact bug this box shipped once already (spans silently
+  dropped for `TextEdit`, found only by screenshotting, not by any test —
+  `markdown.rs`'s own unit tests check string/range logic, which is
+  correct in isolation and proves nothing about whether the render path
+  ever sees it).
+- **Colour is now per-glyph, not per-buffer.** `PlacedGlyph` gained a
+  `color: UiColor` field (from parley's own per-run `Style::brush`), and
+  `Painter::glyphs` draws each glyph in its own colour instead of
+  `RenderedText::color` uniformly. `RenderedText::color` still exists (the
+  buffer's *base* colour, for a caller that wants it as a whole, e.g. to
+  tint a cursor) but no longer drives what a glyph actually renders as.
+
 ## 2026-09-05: accessibility names via AccessKit (RUST.md's I4)
 
 `.label()` (already in `trait_fns.rs`, previously unused anywhere in-tree)