Merge remote-tracking branch 'origin/rustify' into worktree-agent-a9002910a315fe719

docs/IRIS.md

@@ -8,6 +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")
+
+`List` gained `anchor_position_display(&self) -> String`, reporting the
+anchor's own row index and pixel offset (`idx=N/off=Mpx`, or
+`idx=more-before`/`idx=more-after`/`idx=none`) -- what a scripted
+benchmark reads to report fling travel. Note the anchor does not
+necessarily change *slot* over a long scroll (this widget's own documented
+design: the anchor is a stable identity, not re-derived from what's on
+screen each frame), so this is not the same measurement as a Compose
+`LazyListState.firstVisibleItemIndex`, which does track the true topmost
+visible row -- the `off` half is what actually reflects how far a fling
+travelled.
+
+`iris_core::render::frame_report::FrameReport` gained three methods for
+per-phase benchmark reporting: `mark_phase(name)` records a named phase
+boundary at the current frame/instant; `phase_stats(now, refresh_hz)`
+returns one `PhaseStats` (frames, wall duration, late count/percent,
+p50/p90/p99, worst) per marked phase, sliced from the existing ring by a
+new parallel `index_ring`; `late_at_hz(refresh_hz)` gives the whole run's
+late count/percent judged against an arbitrary refresh rate rather than
+the fixed 60Hz `JANK_THRESHOLD` every existing caller still uses (a
+separate method, not a parameter on `report()`, so nothing else changes
+behaviour). `RING_CAPACITY` grew 4096->16384 to hold a full multi-phase
+run without evicting earlier phases' samples.
+
 ## 2026-09-06: `List::fling`, `VelocityTracker`, `FlingCalculator` (IRIS_TODO.md's "swiping has no momentum")
 
 `iris::widget::List` gained a real fling: `fling(velocity_px_per_s)` starts