feat: add keyboard shortcuts and Tab link traversal on pointer hosts

app/lib/presentation/reader/reader_screen.dart

@@ -1,5 +1,8 @@
+import 'package:flutter/foundation.dart'
+    show defaultTargetPlatform, TargetPlatform;
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart' show ScrollDirection;
+import 'package:flutter/services.dart' show LogicalKeyboardKey;
 import 'package:signals/signals_flutter.dart' show SignalBuilder;
 
 import '../../application/controllers/browser_controller.dart'
@@ -32,13 +35,22 @@ class ReaderScreen extends StatefulWidget {
 
 class _ReaderScreenState extends State<ReaderScreen> {
   final _scroll = ScrollController();
+  final _addressFocus = FocusNode();
 
   /// The address bar is on screen from the start, hidden while the reader
-  /// scrolls down, back on any upward scroll.
+  /// scrolls down, back on any upward scroll. A pointer host with a keyboard
+  /// has room to spare and keys to reach the bar, so it never hides.
   bool _chromeVisible = true;
   bool _showBrokenText = false;
   final _checkedSubscriptions = <String>{};
 
+  /// Touch devices navigate with gestures; the others are pointer hosts
+  /// whose readers reach the chrome with the mouse and the keyboard.
+  static bool get _isTouch => switch (defaultTargetPlatform) {
+        TargetPlatform.android || TargetPlatform.iOS => true,
+        _ => false,
+      };
+
   @override
   void initState() {
     super.initState();
@@ -49,10 +61,14 @@ class _ReaderScreenState extends State<ReaderScreen> {
   void dispose() {
     _scroll.removeListener(_onScroll);
     _scroll.dispose();
+    _addressFocus.dispose();
     super.dispose();
   }
 
   void _onScroll() {
+    // On a pointer host the bar stays on screen, so scrolling changes
+    // nothing about it.
+    if (!_isTouch) return;
     if (!_scroll.hasClients) return;
     final position = _scroll.position;
 
@@ -70,7 +86,7 @@ class _ReaderScreenState extends State<ReaderScreen> {
   Widget build(BuildContext context) {
     final deps = AppScope.of(context).deps;
 
-    return Scaffold(
+    final reader = Scaffold(
       body: Column(
         children: [
           AnimatedSlide(
@@ -82,7 +98,7 @@ class _ReaderScreenState extends State<ReaderScreen> {
               curve: Curves.easeOut,
               alignment: Alignment.topCenter,
               child: _chromeVisible
-                  ? const AddressBar()
+                  ? AddressBar(focusNode: _addressFocus)
                   : const SizedBox(width: double.infinity),
             ),
           ),
@@ -134,6 +150,43 @@ class _ReaderScreenState extends State<ReaderScreen> {
         ],
       ),
     );
+
+    // A pointer host drives the reader from the keyboard as well: the bar
+    // takes an address (Ctrl or Cmd+L, which selects what is in it), the page
+    // reloads (Ctrl or Cmd+R), and the walk goes back and forward
+    // (Alt+Left/Right, or Cmd+Left/Right and Cmd+[ and Cmd+] on a Mac).
+    // Touch hosts navigate with gestures instead.
+    if (_isTouch) return reader;
+    return CallbackShortcuts(
+      bindings: {
+        const SingleActivator(LogicalKeyboardKey.keyL, control: true):
+            _addressFocus.requestFocus,
+        const SingleActivator(LogicalKeyboardKey.keyL, meta: true):
+            _addressFocus.requestFocus,
+        const SingleActivator(LogicalKeyboardKey.keyR, control: true):
+            deps.browser.reload,
+        const SingleActivator(LogicalKeyboardKey.keyR, meta: true):
+            deps.browser.reload,
+        const SingleActivator(LogicalKeyboardKey.arrowLeft, alt: true):
+            deps.browser.back,
+        const SingleActivator(LogicalKeyboardKey.arrowRight, alt: true):
+            deps.browser.forward,
+        // The same walk, with the keys a Mac reader reaches for.
+        const SingleActivator(LogicalKeyboardKey.arrowLeft, meta: true):
+            deps.browser.back,
+        const SingleActivator(LogicalKeyboardKey.arrowRight, meta: true):
+            deps.browser.forward,
+        const SingleActivator(LogicalKeyboardKey.bracketLeft, meta: true):
+            deps.browser.back,
+        const SingleActivator(LogicalKeyboardKey.bracketRight, meta: true):
+            deps.browser.forward,
+      },
+      // Key events reach only the focused branch, and a session starts with
+      // nothing focused; this node gives them a place to arrive. Tapping the
+      // address field or a control moves the focus deeper in, where the
+      // shortcuts still apply.
+      child: Focus(autofocus: true, skipTraversal: true, child: reader),
+    );
   }
 
   Widget _body(BuildContext context, MewsPage? page) {