feat(ui): add worker connection help modal

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.Ui/ViewModels/Modals/WorkerConnectionModalViewModel.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Diagnostics;
+using ClaudeDo.Ui.Services;
+using CommunityToolkit.Mvvm.Input;
+
+namespace ClaudeDo.Ui.ViewModels.Modals;
+
+public sealed partial class WorkerConnectionModalViewModel : ViewModelBase
+{
+    private readonly WorkerLocator _workerLocator;
+    private readonly InstallerLocator _installerLocator;
+
+    public WorkerConnectionModalViewModel(WorkerLocator workerLocator, InstallerLocator installerLocator)
+    {
+        _workerLocator = workerLocator;
+        _installerLocator = installerLocator;
+    }
+
+    public Action? CloseAction { get; set; }
+
+    [RelayCommand] private void Close() => CloseAction?.Invoke();
+
+    [RelayCommand]
+    private void StartWorker()
+    {
+        var exe = _workerLocator.Find();
+        if (exe is null) return;
+        try { Process.Start(new ProcessStartInfo(exe) { UseShellExecute = true }); }
+        catch { /* nothing useful to show */ }
+        CloseAction?.Invoke();
+    }
+
+    [RelayCommand]
+    private void RerunInstaller()
+    {
+        var path = _installerLocator.Find();
+        if (path is null) return;
+        try
+        {
+            Process.Start(new ProcessStartInfo(path) { UseShellExecute = true });
+            Environment.Exit(0);
+        }
+        catch { /* nothing useful to show */ }
+    }
+}

src/ClaudeDo.Ui/Views/Modals/WorkerConnectionModalView.axaml

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+<Window xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:vm="using:ClaudeDo.Ui.ViewModels.Modals"
+        xmlns:ctl="using:ClaudeDo.Ui.Views.Controls"
+        x:Class="ClaudeDo.Ui.Views.Modals.WorkerConnectionModalView"
+        x:DataType="vm:WorkerConnectionModalViewModel"
+        Title="Worker not reachable"
+        Width="520" Height="240"
+        WindowDecorations="None"
+        ExtendClientAreaToDecorationsHint="True"
+        WindowStartupLocation="CenterOwner"
+        Background="{DynamicResource SurfaceBrush}">
+  <Window.KeyBindings>
+    <KeyBinding Gesture="Escape" Command="{Binding CloseCommand}"/>
+  </Window.KeyBindings>
+
+  <ctl:ModalShell Title="WORKER NOT REACHABLE" CloseCommand="{Binding CloseCommand}">
+    <Grid RowDefinitions="*,Auto" Margin="20,16">
+      <TextBlock Grid.Row="0" Classes="meta" TextWrapping="Wrap"
+                 Text="ClaudeDo can't reach the background worker. It is normally started automatically at logon. You can start it now, or reinstall if the problem persists."/>
+      <StackPanel Grid.Row="1" Orientation="Horizontal" Spacing="8"
+                  HorizontalAlignment="Right" Margin="0,16,0,0">
+        <Button Classes="btn" Content="Dismiss" Command="{Binding CloseCommand}"/>
+        <Button Classes="btn" Content="Rerun Installer" Command="{Binding RerunInstallerCommand}"/>
+        <Button Classes="btn primary" Content="Start Worker" Command="{Binding StartWorkerCommand}"/>
+      </StackPanel>
+    </Grid>
+  </ctl:ModalShell>
+</Window>

src/ClaudeDo.Ui/Views/Modals/WorkerConnectionModalView.axaml.cs

@@ -0,0 +1,10 @@
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+
+namespace ClaudeDo.Ui.Views.Modals;
+
+public partial class WorkerConnectionModalView : Window
+{
+    public WorkerConnectionModalView() => InitializeComponent();
+    private void InitializeComponent() => AvaloniaXamlLoader.Load(this);
+}