Phone layout: fill the screen in the home-screen app, drop the title row

In the iOS home-screen app the layout viewport - `100dvh`, `innerHeight`, even a
`position: fixed; inset: 0` box - can come back one status bar short, which left the
dock floating that far above the bottom of the screen with an empty strip below it.
In standalone mode the stage now takes its height from `screen` instead (swapped for
landscape, since iOS reports it in portrait), via a `--full-height` variable that
lib/fullHeight.ts sets only there; the keyboard inset is measured against the same
height. A Safari tab, Android and the kiosk are unchanged.

The mascot and app title above the group switch only cost a row on a phone, so they
are gone; the connection/figure pill moves above the group switch, centred, and only
shows while it has something to say.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/main.tsx

@@ -3,6 +3,7 @@ import { createRoot } from "react-dom/client";
 
 import { App } from "./App";
 import { PERF } from "./lib/perfSettings";
+import { installFullHeight } from "./lib/fullHeight";
 import { applySkin } from "./lib/skins";
 import "./styles/app.css";
 import "./styles/mobile.css";
@@ -11,6 +12,7 @@ import "./styles/tippen.css";
 
 // Before the first render, so nothing ever paints in the wrong skin's colours.
 applySkin();
+installFullHeight();
 
 createRoot(document.getElementById("root")!).render(
   <StrictMode>