docs: the two warnings the bench Android build still prints, and why they stand

Both are pre-existing and both are decisions rather than cleanups.
`show_diagnostics_overlay` and the Java overlay behind it are an escape
hatch that draws a report even when iris itself has stopped drawing --
the one case the in-iris diagnostics pane cannot cover -- so deleting
them to clear the warning would remove a fallback, and Iris has no
logcat on her phone.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/IRIS_TODO.md

@@ -901,6 +901,24 @@ diagnosis and what building it actually costs.
   route goes through, and a test per route that a rebuilt card leaves no
   stale handle behind.
 
+## Warnings standing in the bench build (2026-09-08)
+
+Seen while checking `cargo ndk -t arm64-v8a check -p iris-android-app
+--features bench`, pre-existing rather than added by this pass, and left
+rather than silenced because each is a decision:
+
+- [ ] **`PlatformHandle::show_diagnostics_overlay` has no caller.** It
+  and the ~60 lines of `IrisView.showDiagnosticsOverlay` behind it are a
+  plain-`TextView` overlay with Copy and Close, drawn over whatever iris
+  is doing -- built so a report can be read *even if iris itself has
+  stopped drawing*, which is the one case the in-iris diagnostics pane
+  that replaced it cannot cover. So this is a live escape hatch nobody
+  calls, not dead code: deleting both halves clears the warning and
+  removes the fallback, and wiring it back to something is a product
+  decision (Iris has no `logcat` on her phone). Ask before doing either.
+- [ ] **`unused dependency: tabs-ui`.** Already explained in
+  `iris/android-app/Cargo.toml`'s own comment at the `tabs-ui` line.
+
 ## Build (for the port)
 
 Widgets `RUST.md`'s "The port, in order (decided 2026-09-05)" needs and