Merge remote-tracking branch 'origin/rustify' into worktree-agent-afe80868604fef704

# Conflicts:
#	IRIS.md
#	RUST.md

IRIS.md

@@ -30,6 +30,49 @@ let (screen, tree) = transcript_ui::build_tree(rsc, rows);
 some_widget_ptr(rsc).set(tree);
 ```
 
+
+## 2026-09-05: `DragArbiter`, pan-vs-select for one shared touch gesture (RUST.md's I5)
+
+New public type, `iris::sense::DragArbiter`. Why: a widget author who
+registers both a list-level pan and a row-level drag-to-select on the same
+touch gesture has no way to arbitrate between them — `core/src/sense.rs`'s
+`run_sensors` always gives the innermost layer first refusal, so the inner
+one wins every frame it is pressed, not just the frame the press started
+(this is exactly what left transcript-ui's touch-drag panning unreachable
+until now). `DragArbiter` is one small state machine, one instance per
+gesture surface (a whole list, not per row), that a caller drives with its
+own `press_start`/`update`/`release` calls and a caller-supplied `Instant`
+(so it is unit-testable without a real clock or a render harness). It
+decides the way Android itself does: an ordinary vertical drag pans
+immediately; a stationary press held `LONG_PRESS` (500ms) starts a
+selection, which any further drag then extends; a horizontal drag while
+something is already selected extends it immediately, skipping the wait.
+
+```rust
+// One per list, held alongside whatever state coordinates the rows:
+let mut arbiter = DragArbiter::new();
+
+// On press-down:
+arbiter.press_start(pos, Instant::now(), already_selected);
+// Every frame the button/finger stays down:
+match arbiter.update(pos, Instant::now()) {
+    DragOutcome::Pan(dy) => list.scroll(-dy),
+    DragOutcome::SelectStart => selection.begin(...),
+    DragOutcome::SelectExtend => selection.extend(...),
+    DragOutcome::Undecided => {}
+}
+// On release:
+arbiter.release();
+```
+
+`transcript-ui`'s `Selection::drag` (`transcript-ui/src/selection.rs`) is
+the reference caller: every row's `CursorSense::click_or_drag() |
+CursorSense::unclick()` handler routes through one `Selection`-owned
+arbiter instead of calling `begin`/`extend` directly, so a drag that starts
+on a row's own rendered text now pans the list correctly instead of
+always starting a selection. 8 new unit tests in `iris/src/sense.rs`'s
+`drag_arbiter_tests` module.
+
 ## 2026-09-05: `SpanStyle`, per-range text styling (RUST.md's I5)
 
 A `TextBuffer` used to have exactly one style (`TextAttrs`: colour, size,