feat(worker): run worker as per-user logon task instead of Windows service

A LocalSystem Windows service can't see the logged-in user's Claude CLI
authentication, so the worker now runs as the current user via a hidden
per-user logon Scheduled Task with restart-on-failure.

- Worker is WinExe (no console window) with a Serilog rolling file sink and
  a single-instance mutex so the logon task, app ensure-running, and Restart
  button can't fight over the SignalR port.
- Installer replaces the service steps (register/start/stop) with autostart
  task steps, migrates the legacy ClaudeDoWorker service away on update, and
  removes the task on uninstall. ServicePage drops the service-account UI.
- UI gains a WorkerLocator; the app ensures the worker is running at startup
  and the Restart button kills+relaunches this install's worker process.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ClaudeDo.Installer/Steps/RegisterAutostartStep.cs

@@ -0,0 +1,59 @@
+using System.IO;
+using System.Security.Principal;
+using ClaudeDo.Installer.Core;
+
+namespace ClaudeDo.Installer.Steps;
+
+public sealed class RegisterAutostartStep : IInstallStep
+{
+    public const string TaskName = "ClaudeDoWorker";
+    private const string LegacyServiceName = "ClaudeDoWorker";
+
+    public string Name => "Register Autostart";
+
+    public async Task<StepResult> ExecuteAsync(InstallContext ctx, IProgress<string> progress, CancellationToken ct)
+    {
+        var workerExe = Path.Combine(ctx.InstallDirectory, "worker", "ClaudeDo.Worker.exe");
+        if (!File.Exists(workerExe))
+            return StepResult.Fail($"Worker executable not found: {workerExe}");
+
+        // 1) Migrate away the legacy Windows service if present.
+        progress.Report("Checking for legacy worker service...");
+        var (queryExit, _) = await ProcessRunner.RunAsync("sc.exe", $"query {LegacyServiceName}", null, progress, ct);
+        if (queryExit == 0)
+        {
+            progress.Report("Removing legacy worker service...");
+            await ProcessRunner.RunAsync("sc.exe", $"stop {LegacyServiceName}", null, progress, ct);
+            await ProcessRunner.RunAsync("sc.exe", $"delete {LegacyServiceName}", null, progress, ct);
+            for (var i = 0; i < 30; i++)
+            {
+                ct.ThrowIfCancellationRequested();
+                var (q, _) = await ProcessRunner.RunAsync("sc.exe", $"query {LegacyServiceName}", null, progress, ct);
+                if (q != 0) break;
+                await Task.Delay(1000, ct);
+            }
+        }
+
+        // 2) Register (or replace) the per-user logon task.
+        var userId = WindowsIdentity.GetCurrent().Name;
+        var minutes = Math.Max(1, ctx.RestartDelayMs / 60000);
+        var xml = ScheduledTaskXml.Build(userId, workerExe, minutes);
+
+        var xmlPath = Path.Combine(Path.GetTempPath(), $"ClaudeDoWorker-{Guid.NewGuid():N}.xml");
+        await File.WriteAllTextAsync(xmlPath, xml, new System.Text.UnicodeEncoding(false, true), ct);
+        try
+        {
+            progress.Report("Registering logon task...");
+            var (exit, output) = await ProcessRunner.RunAsync(
+                "schtasks.exe", $"/Create /TN \"{TaskName}\" /XML \"{xmlPath}\" /F", null, progress, ct);
+            if (exit != 0)
+                return StepResult.Fail($"schtasks /Create failed (exit {exit}): {output}");
+        }
+        finally
+        {
+            try { File.Delete(xmlPath); } catch { /* best effort */ }
+        }
+
+        return StepResult.Ok();
+    }
+}