irisandClaude Opus 5
00e0a63887
For the next session, since this one is about to be cleared. Current design only -- `Scroll` owns the position, the gesture and the fling; a child is either moved or answers `Widget::scrolls_itself` and is handed deltas; one sign convention, the finger's. It carries the things that are expensive to rediscover and easy to undo by accident: why the two `&self` capability methods must not be `&mut` (`get_dyn_mut` marks dirty), why `scroll_offset` exists beside `apply_scroll`'s remainder, why the measuring draw is free, why nothing is marked by hand, why the height cache stays in the container, why the transcript builds its `Scroll` by hand instead of through `.scrollable_to_end()`, and the measured numbers behind "a `LazySpan` is not a `Span`". Also names the one thing still open -- the pin -- with the two ways to close it and an instruction to ask Iris rather than guess. `scroll.rs` and `lazy_span.rs` now point at it from their module docs rather than restating it, AGENTS.md lists it beside the other design documents, and IRIS_TODO.md's in-progress entry defers to it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>