Fix Windows auto-update to replace Navis.exe in place (1.8.1).

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/update/update_other.go

@@ -13,3 +13,6 @@ func Apply(ctx context.Context, manifestURL string) (string, error) {
 	_ = manifestURL
 	return "", fmt.Errorf("автообновление пока только для Windows и macOS")
 }
+
+// CleanupStaleDownloads is a no-op on unsupported platforms.
+func CleanupStaleDownloads() {}