iris: fix I2's render gap -- window uniform never left (0, 0) on android-view

UiRenderNode::new seeded the GPU window uniform from
WindowUniform::default() rather than the surface's real size, so
shader.wgsl's vertex stage divided every primitive's position by
(0, 0) and produced NaN/Inf clip coordinates on both Vulkan and GLES.
winit's backend never hit this because winit fires an initial
WindowEvent::Resized that corrects the uniform before the first frame;
android-view has no equivalent event, so the node it built never got
corrected. Seed the uniform from the SurfaceConfiguration passed to
UiRenderNode::new instead, which is already right on both backends at
construction time.

Verified on the ai-app-2 emulator (Vulkan/SwiftShader and, temporarily
forced, GLES/virgl): the tabs example now draws its widgets instead of
just the clear colour. Ticks I2 in RUST.md.

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

iris/core/src/render/mod.rs

@@ -201,7 +201,21 @@ impl UiRenderNode {
             source: ShaderSource::Wgsl(SHAPE_SHADER.into()),
         });
 
-        let window_uniform = WindowUniform::default();
+        // Seeded from the surface's own size, not `WindowUniform::default()`
+        // (0, 0): the vertex shader divides by `window.dim` to reach clip
+        // space, so a window this buffer disagrees with means every
+        // primitive's position is NaN/Inf and is dropped before
+        // rasterization -- the clear colour still reaches the screen (the
+        // pass runs regardless) while nothing drawn on top of it ever does.
+        // winit's backend gets away with the old default because winit
+        // fires an initial `WindowEvent::Resized` that calls `resize()`
+        // before the first frame; android-view has no such automatic
+        // event, so `AndroidRenderer::new` built a node whose window buffer
+        // was never corrected -- this is I2's "nothing draws" bug (RUST.md).
+        let window_uniform = WindowUniform {
+            width: config.width as f32,
+            height: config.height as f32,
+        };
         let window_buffer = device.create_buffer_init(&BufferInitDescriptor {
             label: Some("window"),
             contents: bytemuck::cast_slice(&[window_uniform]),