docs: close I5's three blocked verifications (24/24-swipe, backend isolation, cold-boot bench)

Ran three clean iris-scroll.sh passes on a cold -gpu host boot (all
24/24 swipes confirmed scrolling via clustered render() timestamps, not
inferred from frame count) and retook the host-GPU table's iris row as
a best-of-three. EMU_GPU=software + force-gles still cannot produce a
GLES number on this hardware -- after the earlier compute-limit crash
was fixed, device creation now aborts on max_storage_buffer_binding_size
instead (SwiftShader ES 3.0 has no SSBOs, and shader.wgsl reads four
var<storage> buffers unconditionally), so the SwiftShader-Vulkan-vs-GLES
question is closed as structurally unanswerable rather than answered.
A fresh cold-boot run-bench.sh reading for P0's bench build is in line
with the earlier warm-AVD readings, closing that box's own caveat too.

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

docs/DECISIONS.md

@@ -264,24 +264,30 @@ marked **DEFERRED** are ones the agent chose not to decide alone.
   | app | build | GPU mode | frames | janky % | p50 | p90 | p99 | worst | cpu p50 | gpu-wait p50 |
   |---|---|---|---|---|---|---|---|---|---|---|
   | Compose (in-app report) | debug | host (virgl) | 1268 | 96.4% late | 20.0ms | 28.4ms | 37.7ms | -- | -- | -- |
-  | iris (`FrameReport`) | **release**, `force-gles` | host (virgl) | 62 | 41.94% | 15.0ms | 21.8ms | 37.1ms | 37.1ms | 0.2ms | 12.9ms |
+  | iris (`FrameReport`), **best of three, 2026-09-05** | release, `force-gles` | host (virgl) | 439 | 46.24% | 15.7ms | 23.3ms | 31.2ms | 57.4ms | 1.2ms | 13.2ms |
 
   Under real GPU rendering iris's median frame is *faster* than
   Compose's, not the 2-3x-slower shape the software-mode table shows. A
   new split inside `FrameReport` (redraw-to-submit vs. submit-to-present,
   commit `e2a1fad`) says why: iris's own CPU work per frame is a median
-  0.2ms -- almost the entire frame is time spent handing the frame to the
+  ~1ms -- almost the entire frame is time spent handing the frame to the
   driver, not in iris's layout/text/primitive code. This is consistent
   with the earlier software-mode gap being mostly SwiftShader's CPU
-  rasterisation cost rather than an iris-specific slowness, but is not
-  proof of it: a same-mode software `force-gles` run to isolate the
-  backend crashed for an unrelated reason (SwiftShader's GL path reports
-  itself as OpenGL ES 3.0, which has no compute shaders, and iris's device
-  request assumes them unconditionally) — real scope to fix, not done
-  here — and the two apps' frame populations still differ in kind the same
-  way the software-mode caveats describe. A real intermittent touch-
-  scroll dropout was also reproduced this pass (six consecutive swipes
-  produced zero redraws while taps kept working; an identical retry then
-  succeeded) and is not explained. RUST.md's I5 box, "Where iris's frame
-  time goes, 2026-09-05, the `-gpu host` pass," has the full account. The
-  iris-vs-Masonry choice itself is still Iris's to make.
+  rasterisation cost rather than an iris-specific slowness. **Still not
+  proof, and now closed as unanswerable rather than merely untaken**: a
+  same-mode software `force-gles` run to isolate the backend was retried
+  2026-09-05 after fixing the compute-limit crash the first attempt hit,
+  and hit a second, structural wall instead — SwiftShader's ES 3.0 GL
+  path has no storage-buffer capacity at all, and `shader.wgsl` reads
+  `var<storage>` buffers unconditionally, so reaching that path needs a
+  shader rewrite, not a limits fix (RUST.md's I5 box, "The three
+  remaining I5 verifications, closed 2026-09-05," item 2). The
+  intermittent touch-scroll dropout this pass also reproduced is
+  root-caused and fixed as of the same date (a missed `ACTION_DOWN` on a
+  row's padding/header left `DragArbiter` stuck in `Idle`); three clean
+  `iris-scroll.sh` runs post-fix each scrolled all 24/24 swipes, replacing
+  the single-attempt 62-frame reading this table used to carry. RUST.md's
+  I5 box, "Where iris's frame time goes, 2026-09-05, the `-gpu host`
+  pass," and "The three remaining I5 verifications, closed 2026-09-05,"
+  have the full account. The iris-vs-Masonry choice itself is still
+  Iris's to make.