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>

CHANGELOG.md

@@ -3,6 +3,15 @@
 All notable changes to CodeCraft. Versions follow [Semantic Versioning](https://semver.org/);
 until 1.0, minor versions may contain breaking changes.
 
+## [Unreleased]
+
+### Fixed
+
+- **Phone: page stayed shifted after the keyboard closed** – the top bar (menu) was out of
+  reach. On Android the keyboard now shrinks the page instead of shifting it
+  (`interactive-widget=resizes-content`; the chat stays at its latest message); browsers that
+  still shift the page (iOS Safari) get it scrolled back once the keyboard closes.
+
 ## [v202611-00015] – 2026-11-10
 
 ### Fixed