docs: the defect pass's findings -- RUST.md boxes, IRIS_TODO ticks, DECISIONS and IRIS entries

docs/IRIS.md

@@ -8,7 +8,31 @@ 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: `List::anchor_position_display`, `FrameReport::mark_phase`/`phase_stats`/`late_at_hz` (RUST.md's "Benchmark v2")
+## 2026-09-06: a tap on a text field always leaves a caret
+
+`TextEditCtx::select` used to compare the tap position against the
+*laid-out text's* own box and set `selection = None` for anything outside
+it. A press only reaches `select` after being hit-tested to the widget, so
+that "outside" meant the field's own padding -- or, for an **empty** field,
+everything, since an empty layout is a zero-width box. So tapping an empty
+composer focused it and opened the keyboard while leaving no caret, and
+`TextEditCtx::insert`/`insert_str` return early with no caret: every
+keystroke was dropped in silence, and no glyph ever appeared. Parley's
+`from_point`/`extend_to_point` already clamp a point outside the layout to
+the nearest cursor position, which is also what a tap in a field's padding
+should do.
+
+Behaviour change a caller would notice, in one line: **`select` with a
+non-drag position now always produces a selection; it no longer clears
+one.** Clearing is `TextEditCtx::deselect`, which is what the backends'
+focus handling already calls. A drag is unchanged -- with no previous
+selection there is still nothing to extend, so it produces none.
+
+`insert_str` also gained a `debug_assert!` for the no-caret case, so an
+insert routed to an unfocused field fails at the mistake in a debug build
+instead of silently swallowing input.
+
+## 2026-09-06: `List::anchor_position_display`## 2026-09-06: `List::anchor_position_display`, `FrameReport::mark_phase`/`phase_stats`/`late_at_hz` (RUST.md's "Benchmark v2")
 
 `List` gained `anchor_position_display(&self) -> String`, reporting the
 anchor's own row index and pixel offset (`idx=N/off=Mpx`, or