Move the instrumentation off the header and into About

The render backend, the layout class and the frame rate sat permanently in a
44px strip that also carries the only way out of develop, the undo pair, the
panel toggle and the export button. They cost about 200 logical pixels, and a
`HorizontalLayout` given less width than its children's minimums does not
shrink them — it runs off the end.

There was already a breakpoint hiding them below 820px, which is why a tablet
in portrait (768) looked fine and landscape (1200) did not: above the
breakpoint the readouts came back and pushed the header off the right-hand
edge. A breakpoint that hides a problem at one size and not another is a
workaround, and this removes the reason for it rather than moving it.

They are diagnostics — read once when something looks wrong, and then not
again — so they are in Settings under ABOUT, beside the version, which is
where someone goes when they have a bug to report rather than a photograph to
edit. The version is there for the same reason and comes from
`CARGO_PKG_VERSION`, so the line cannot disagree with the binary showing it.

The frame rate keeps its warning hue. It is the number that says whether the
zero-copy display path is holding up, which is the assumption the whole
display design rests on, and that is worth colour wherever it is shown.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ui/dr-ui/src/lib.rs

@@ -764,6 +764,10 @@ pub fn run(paths: Vec<PathBuf>) -> Result<()> {
     let gpu = shared_gpu();
 
     let window = AppWindow::new()?;
+    // The version the About page shows. Taken from the crate rather than
+    // passed in, so it is the version of the code that is running and cannot
+    // be set to something else by a caller.
+    window.set_app_version(env!("CARGO_PKG_VERSION").into());
     match &gpu {
         Some(ctx) => {
             log::info!("adapter: {} ({:?})", ctx.adapter_name(), ctx.backend());