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/WriteUninstallRegistryStep.cs

@@ -26,14 +26,22 @@ public sealed class WriteUninstallRegistryStep : IInstallStep
         // the single-file temp extract is gone once this process exits.
         var sourceExe = Environment.ProcessPath
             ?? throw new InvalidOperationException("Cannot resolve running installer path.");
-        try
+        // In the self-update path the installer already runs from uninstaller/ (the
+        // --replace-self handoff put it there), so source == target and the copy would
+        // throw. Skip it; the binary is already in place.
+        var alreadyInPlace = string.Equals(
+            Path.GetFullPath(sourceExe), Path.GetFullPath(targetExe), StringComparison.OrdinalIgnoreCase);
+        if (!alreadyInPlace)
         {
-            progress.Report("Copying uninstaller binary...");
-            File.Copy(sourceExe, targetExe, overwrite: true);
-        }
-        catch (Exception ex)
-        {
-            return StepResult.Fail($"Failed to copy uninstaller exe: {ex.Message}");
+            try
+            {
+                progress.Report("Copying uninstaller binary...");
+                File.Copy(sourceExe, targetExe, overwrite: true);
+            }
+            catch (Exception ex)
+            {
+                return StepResult.Fail($"Failed to copy uninstaller exe: {ex.Message}");
+            }
         }
 
         progress.Report("Writing Add/Remove Programs entry...");