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/DownloadAndExtractStep.cs

@@ -44,9 +44,18 @@ public sealed class DownloadAndExtractStep : IInstallStep
             var zipPath = Path.Combine(scratchDir, zipAsset.Name);
             var checksumPath = Path.Combine(scratchDir, "checksums.txt");
 
-            progress.Report($"Downloading {zipAsset.Name} ({zipAsset.Size / (1024 * 1024)} MB)...");
+            var totalMb = zipAsset.Size / (1024 * 1024);
+            progress.Report($"Downloading {zipAsset.Name} ({totalMb} MB)...");
+            long lastReportedMb = -1;
             await _releases.DownloadAsync(zipAsset.BrowserDownloadUrl, zipPath,
-                new Progress<long>(b => progress.Report($"  {b / (1024 * 1024)} MB downloaded")),
+                new Progress<long>(b =>
+                {
+                    var mb = b / (1024 * 1024);
+                    if (mb == lastReportedMb) return;
+                    lastReportedMb = mb;
+                    // Leading "\r" tells the UI to overwrite the previous line instead of appending.
+                    progress.Report($"\r  {mb} / {totalMb} MB downloaded");
+                }),
                 ct);
 
             progress.Report("Downloading checksums...");