iris/android-app: opaque header background, header sizes onto dp

Iris's phone report (build a9232ac): "the header buttons have nothing
behind them and overlap the transcript text." Only each button's own
rect painted anything, so the gaps between and around them (and the
status-bar strip above) showed CLEAR_COLOR (black) one layer back, and
the row's reserved height was three abs (physical-pixel) button boxes --
smaller, on a dense phone, than the dp-correct size the transcript below
now uses post the previous two commits, which is what reads as overlap
once the two disagree.

Fixed with a HEADER_SURFACE rect stacked behind the whole button row
(not just behind each button), and every non-text size in the header
(button padding, row height, the report field's padding) moved from a
bare number to dp(...), so the row's reserved height in the outer
Span::DOWN matches what is actually painted. The list/report field
already sit below the header in that same Span::DOWN, not behind it --
no stacking change needed there.

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

iris/android-app/src/bench_client.rs

@@ -184,7 +184,7 @@ impl AndroidAppState for BenchClient {
         let tree = (
             top_bar,
             content.height(rest(2)),
-            report_display.height(rest(1)).pad(8),
+            report_display.height(rest(1)).pad(dp(8)),
         )
             .span(Dir::DOWN)
             .add_strong(rsc)
@@ -246,7 +246,11 @@ impl AndroidAppState for BenchClient {
     /// Pads the top button row by the status-bar inset -- see `top_bar`'s
     /// field comment. Rebuilds the row rather than mutating a stored
     /// `Padding` in place, since nothing here holds a handle to one.
-    fn on_insets_changed(&mut self, rsc: &mut AndroidRsc<Self>, insets: iris::android::LogicalInsets) {
+    fn on_insets_changed(
+        &mut self,
+        rsc: &mut AndroidRsc<Self>,
+        insets: iris::android::WindowInsets,
+    ) {
         let controls = bench_controls(rsc, insets.top);
         (self.top_bar)(rsc).set(controls);
     }
@@ -254,11 +258,33 @@ impl AndroidAppState for BenchClient {
 
 type Rsc = AndroidRsc<BenchClient>;
 
-/// `top_pad` is the status-bar inset in logical units (0.0 until
+/// The header row's own backdrop -- see `bench_controls`'s doc comment on
+/// why it needs one at all. A dark neutral rather than pure black
+/// (`android::render::CLEAR_COLOR`) so the row reads as a distinct panel
+/// instead of a hole in the background the buttons happen to float in.
+const HEADER_SURFACE: UiColor = UiColor::new(28, 28, 34, 255);
+
+/// `top_pad` is the status-bar inset in physical pixels (0.0 until
 /// `on_insets_changed` has run once) -- folded in here, rather than
 /// exposing the unadded builder for a caller to `.pad()` itself, because
 /// naming that builder's type at each call site is more machinery than a
 /// top-of-screen padding number is worth.
+///
+/// **Backed by an opaque rect the full size of the row, not just the three
+/// buttons.** Iris's phone report (docs/RUST.md's P0 box, screenshots on
+/// build a9232ac): "the header buttons have nothing behind them and
+/// overlap the transcript text" -- before this, only each button's own
+/// `rect(...)` painted anything, so the gaps between and around them (and
+/// the status-bar strip above them) showed whatever was one layer back
+/// (`CLEAR_COLOR`, black), and the row's true height was three
+/// physical-pixel-sized (`abs`, not `dp`) button boxes rather than the
+/// density-correct size the transcript below was already using post-P0 --
+/// exactly what reads as "overlap" once the two disagree. Fixed two ways
+/// together: a `HEADER_SURFACE` rect stacked behind the whole row (this
+/// function), and every size below moved from a bare number (physical
+/// pixels) to `dp(...)` (IRIS_TODO.md's density-independent length unit),
+/// so the row's reserved height in the outer `Span::DOWN`
+/// (`AndroidAppState::new`) matches what is actually painted.
 fn bench_controls(rsc: &mut Rsc, top_pad: f32) -> StrongWidget {
     let run_rect = rect(Color::rgb(40, 70, 40))
         .on(
@@ -273,7 +299,7 @@ fn bench_controls(rsc: &mut Rsc, top_pad: f32) -> StrongWidget {
         wtext("Run benchmark").size(18).text_align(Align::CENTER),
     )
         .stack()
-        .pad(8)
+        .pad(dp(8))
         .add(rsc);
 
     let copy_rect = rect(Color::rgb(50, 50, 60))
@@ -289,7 +315,7 @@ fn bench_controls(rsc: &mut Rsc, top_pad: f32) -> StrongWidget {
         wtext("Copy report").size(18).text_align(Align::CENTER),
     )
         .stack()
-        .pad(8)
+        .pad(dp(8))
         .add(rsc);
 
     let diag_rect = rect(Color::rgb(60, 45, 70))
@@ -305,12 +331,14 @@ fn bench_controls(rsc: &mut Rsc, top_pad: f32) -> StrongWidget {
         wtext("Diagnostics").size(18).text_align(Align::CENTER),
     )
         .stack()
-        .pad(8)
+        .pad(dp(8))
         .add(rsc);
 
-    (run, copy, diagnostics)
-        .span(Dir::RIGHT)
-        .height(56)
+    let buttons = (run, copy, diagnostics).span(Dir::RIGHT).add(rsc);
+
+    (rect(HEADER_SURFACE), buttons)
+        .stack()
+        .height(dp(56))
         .pad(Padding::top(top_pad))
         .add_strong(rsc)
         .any()