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/link/net.dart

@@ -0,0 +1,42 @@
+// Android only: binding the process to the USB (NCM) Ethernet link to the Orin.
+// See MainActivity.kt for why Android needs telling.
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+
+class UsbLink extends ChangeNotifier {
+  static const _ch = MethodChannel('yukart/net');
+
+  bool supported = Platform.isAndroid;
+  bool up = false;
+  bool bound = false;
+
+  /// Development hook: a link test requested by launch intent (see MainActivity.kt).
+  void Function(String label)? onLinkTest;
+
+  UsbLink() {
+    if (!supported) return;
+    _ch.setMethodCallHandler((call) async {
+      if (call.method == 'ethernet') {
+        final a = Map<String, dynamic>.from(call.arguments as Map);
+        up = a['up'] == true;
+        bound = a['bound'] == true;
+        notifyListeners();
+      } else if (call.method == 'linktest') {
+        onLinkTest?.call(call.arguments as String);
+      }
+    });
+  }
+
+  /// A link test requested by the intent that launched the app, once.
+  Future<String?> takeLinkTest() async => supported ? _ch.invokeMethod<String>('takeLinkTest') : null;
+
+  /// Bind only when the target is on the USB link; a workstation over WiFi must stay reachable.
+  Future<void> bindFor(Uri target) async {
+    if (!supported) return;
+    final want = target.host.startsWith('192.168.55.');
+    await _ch.invokeMethod<bool>('bindEthernet', want);
+  }
+}