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/widgets/mock_banner.dart

@@ -0,0 +1,28 @@
+// Mock data must look like mock data: on the surface of every page, not in a menu.
+
+import 'package:flutter/material.dart';
+
+import '../theme/palette.dart';
+
+class MockBanner extends StatelessWidget {
+  const MockBanner({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final p = AppTheme.of(context);
+    return Container(
+      color: p.caution,
+      padding: const EdgeInsets.symmetric(vertical: 6),
+      child: Text(
+        'MOCK DATA — NOT FROM THE CAR',
+        textAlign: TextAlign.center,
+        style: TextStyle(
+          color: p.onFill(p.caution),
+          fontWeight: FontWeight.w900,
+          fontSize: 20,
+          letterSpacing: 2,
+        ),
+      ),
+    );
+  }
+}