App structure: a swipe-in menu shell; pages/, link/, actions/; Settings

The shell (shell.dart): a drawer from the left edge or each page's menu button.
Dash, Signals, Captures; Tools (Camera, Link test, Orin power options), the
rarely used ones, after pirate-station-aide; Settings (gateway address, dark/bright,
build-time theme and landing). Landing view at build time: YUKART_HOME=dash|signals,
signals for now. Dash, Signals and Captures stay alive while hidden; Captures has its
own navigator, so a run survives switching views. Back goes inside Captures, then to
the landing view, then out. The mock banner sits over every page.

main.dart is startup only; the old home screen is pages/signals.dart; dialogs and
sheets moved to actions/; the protocol client, USB binding and Reading to link/.
lib/README.md catalogues it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

lib/shell_scope.dart

@@ -0,0 +1,47 @@
+// What a page needs from the shell (lib/shell.dart), without importing it: open the
+// menu, switch view. Pages import this; the shell imports the pages.
+
+import 'package:flutter/material.dart';
+
+/// Every view the menu offers. Tools are the rarely used ones (pirate-station-aide's pattern).
+enum ShellView { dash, signals, captures, camera, linkTest, settings }
+
+/// The landing view, set at build time: `--dart-define=YUKART_HOME=dash` for the car,
+/// `signals` (the default, for now) while developing.
+ShellView get landingView => switch (const String.fromEnvironment(
+  'YUKART_HOME',
+  defaultValue: 'signals',
+)) {
+  'dash' => ShellView.dash,
+  _ => ShellView.signals,
+};
+
+/// The view on screen. The shell listens to it; anything may set it (the link-test hook does).
+final shellView = ValueNotifier<ShellView>(landingView);
+
+class ShellScope extends InheritedWidget {
+  const ShellScope({super.key, required this.openMenu, required super.child});
+
+  final VoidCallback openMenu;
+
+  static ShellScope? maybeOf(BuildContext context) =>
+      context.dependOnInheritedWidgetOfExactType<ShellScope>();
+
+  @override
+  bool updateShouldNotify(ShellScope old) => false;
+}
+
+/// The menu button every page puts where a back arrow would be. The menu also opens
+/// with a swipe in from the left edge.
+class MenuButton extends StatelessWidget {
+  const MenuButton({super.key, this.color});
+
+  final Color? color;
+
+  @override
+  Widget build(BuildContext context) => IconButton(
+    tooltip: 'Menu',
+    icon: Icon(Icons.menu, color: color),
+    onPressed: ShellScope.maybeOf(context)?.openMenu,
+  );
+}