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/actions/server_url.dart

@@ -0,0 +1,29 @@
+import 'package:flutter/material.dart';
+
+import '../link/boundary.dart';
+import '../link/net.dart';
+
+/// Ask for the gateway's address and reconnect there, binding to the USB link when it is on it.
+Future<void> editUrl(BuildContext context, Boundary b, UsbLink usb) async {
+  final c = TextEditingController(text: b.url);
+  final url = await showDialog<String>(
+    context: context,
+    builder: (ctx) => AlertDialog(
+      title: const Text('Gateway address'),
+      content: TextField(controller: c, autofocus: true),
+      actions: [
+        TextButton(
+          onPressed: () => Navigator.pop(ctx),
+          child: const Text('Cancel'),
+        ),
+        TextButton(
+          onPressed: () => Navigator.pop(ctx, c.text.trim()),
+          child: const Text('Connect'),
+        ),
+      ],
+    ),
+  );
+  if (url == null || url.isEmpty) return;
+  await usb.bindFor(Uri.parse(url));
+  b.retarget(url);
+}