docs: phone report 2026-09-07 later -- overscroll, low initial fling velocity, input/timing report; queued

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/IRIS_TODO.md

@@ -955,3 +955,43 @@ do not duplicate it there.
   the header's bottom must be masked. Fix both with one rule: a row is
   drawn if any part of it intersects the viewport, and the viewport is
   the list's own region.
+
+## From the phone, 2026-09-07, later (build from 4274b8b, ai-app-bench b47eb73)
+
+- [ ] **"You shouldn't be able to scroll below the bottom (or above
+  top)."** The list's offset is not clamped to its content range while
+  dragging and/or flinging. Compose's `LazyColumn` never moves content
+  past its ends -- the overscroll *effect* on Android 12+ is a stretch
+  drawn over clamped content, not a displacement. Clamp the offset in
+  one place (`List`'s scroll setter, so drag, fling, page-in and
+  programmatic scroll all go through it) and end a fling that hits the
+  clamp. Test at layer 1: a drag past either end leaves the offset at
+  the end; a fling into the end stops there.
+- [ ] **"Flinging now actually works but is slower than Compose's
+  immediately after releasing the flick (the slow down seems
+  correct)."** The curve is right, so the *initial velocity* is low.
+  iris's `VelocityTracker::velocity` is total motion over the window's
+  span -- an average -- where Compose's `VelocityTracker` (`compose.ui`
+  `VelocityTracker.kt`, `VelocityTracker1D` with `Strategy.Impulse`,
+  100ms horizon, 20 samples, `AssumePointerMoveStoppedMilliseconds =
+  40`) weights the last samples, so a flick that accelerates into the
+  release reads faster. Port the impulse strategy from source with
+  checked-in reference values from an independent transcription, as
+  the spline was; also apply Compose's min/max fling velocity
+  (`ViewConfiguration`'s 50dp/s and 8000dp/s) so a slow release does
+  not fling and a wild one is capped. Layer-1 test on
+  `flick-120hz.touch` asserting the number Compose's code gives.
+- [ ] **Input-event and timing report from the phone.** Iris: "add
+  another button to copy input event info so that I can do some stuff
+  manually and then send the event log to you ... instrument a lot of
+  the code with timings so I can give you time reports through the
+  same button." Build on the log ring (queue: logging through Dev
+  Updater), not beside it: every `MotionEvent` (action, pointer
+  position, event time, historical sample count) and every gesture
+  decision (`iris drag release:` and its siblings) at debug level into
+  the ring; frame timings (input handled -> layout -> draw submitted,
+  and the fling tick's `now` against the frame clock) at debug level
+  into the same ring; "Copy report" already appends the ring. Add a
+  second button only if the report gets too long to paste -- then
+  "Copy input log" copies the ring alone. Says which build it came
+  from.

docs/RUST.md

@@ -240,6 +240,11 @@ closes it.
   rest of her phone shows (UI_RULES "show what the reader already sees
   elsewhere"), at the cost of the app no longer looking identical on
   every device. Not done without her verdict.
+- [ ] Scroll clamped at both ends, and Compose's impulse velocity
+  estimator with min/max fling velocity (docs/IRIS_TODO.md, 2026-09-07
+  later). After the culling fix lands (same file).
+- [ ] Input-event and timing instrumentation into the log ring, copied
+  by the report button. After the logging route lands (same ring).
 - [ ] Masks with a shape -- docs/LAYOUT.md "Masks with a shape (decided
   2026-09-07)". A mask references a primitive already drawn
   (rect SDF, texture or glyph alpha), chained and multiplied; `.masked()`