Phone: keyboard no longer leaves the page shifted

Mobile browsers scroll the whole page up to show the focused input and do not
always scroll it back when the keyboard closes; the app never scrolls the page
itself, so the top bar (menu) stayed out of reach.

- Viewport interactive-widget=resizes-content: on Android the keyboard shrinks
  the page instead of shifting it.
- Elsewhere (iOS Safari) the page offset is undone when the visual viewport
  grows again or the input loses focus.
- The chat keeps following the latest message when its pane shrinks.

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

web/index.html

@@ -2,7 +2,9 @@
 <html lang="en">
   <head>
     <meta charset="UTF-8" />
-    <meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover" />
+    <!-- interactive-widget: the on-screen keyboard shrinks the page (Android) instead of
+         shifting it up – the top bar stays in place. -->
+    <meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover, interactive-widget=resizes-content" />
     <meta name="theme-color" content="#282828" />
     <link rel="icon" href="/icon.svg" type="image/svg+xml" />
     <link rel="apple-touch-icon" href="/apple-touch-icon.png" />