fix(installer,worker): service hosting, dark theme, uninstall polish

Worker:
- Wire UseWindowsService + Microsoft.Extensions.Hosting.WindowsServices so
  SCM's Service Control Protocol handshake succeeds. Previously the binary
  exited immediately under sc start, leaving the service registered but
  never running.

Installer:
- Pin SDK to .NET 9 (global.json) — SDK 10 dropped win-arm from its RID
  graph, breaking restore of the WPF project; .NET 9 keeps win-arm AND
  understands the .slnx solution format.
- Force SelfContained=true and default RID=win-x64 when PublishSingleFile
  is set, so Rider Publish and CLI produce the same bundle.
- Dark theme: set Background/Foreground explicitly on WizardWindow and
  SettingsWindow roots (WPF implicit styles don't cascade to derived
  Window types). Custom ComboBox template + ComboBoxItem style so
  dropdowns honour the dark palette instead of system defaults.
- Throttle download progress to one report per MB and overwrite the same
  UI line (\r prefix marker) instead of appending per chunk.
- Register ClaudeDo in HKLM\...\Uninstall so it appears in Apps & Features.
  Copy installer into InstallDir\uninstaller\ for the UninstallString, and
  schedule a cmd.exe trampoline to handle the self-delete case when
  Apps & Features launches the copy from inside the install dir.
- Treat sc.exe stop exit 1062 (ERROR_SERVICE_NOT_ACTIVE) as success.
- Delete the uninstall registry key during UninstallRunner.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Installer/Steps/StopServiceStep.cs

@@ -27,6 +27,12 @@ public sealed class StopServiceStep : IInstallStep
         }
 
         var (stopExit, _) = await ProcessRunner.RunAsync("sc.exe", $"stop {ServiceName}", null, progress, ct);
+        // 1062 = ERROR_SERVICE_NOT_ACTIVE — registered but not running, treat as already stopped.
+        if (stopExit == 1062)
+        {
+            progress.Report("Service was registered but not running.");
+            return StepResult.Ok();
+        }
         if (stopExit != 0)
             return StepResult.Fail($"sc.exe stop failed with exit code {stopExit}");