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

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

internal/update/update_darwin.go

@@ -49,3 +49,14 @@ func Apply(ctx context.Context, manifestURL string) (string, error) {
 func shellQuote(s string) string {
 	return "'" + strings.ReplaceAll(s, "'", `'\''`) + "'"
 }
+
+// CleanupStaleDownloads removes leftover update temps from failed/old runs.
+func CleanupStaleDownloads() {
+	exe, err := os.Executable()
+	if err != nil {
+		return
+	}
+	exe, _ = filepath.Abs(exe)
+	_ = os.Remove(exe + ".new")
+	_ = os.Remove(filepath.Join(filepath.Dir(exe), ".navis-update-download"))
+}