test: verify and document desktop ui

src/javis/ui/app.py

@@ -2,9 +2,11 @@
 
 from __future__ import annotations
 
+import os
 import sys
 from collections.abc import Sequence
 
+from PySide6.QtCore import QTimer
 from PySide6.QtWidgets import QApplication, QMessageBox
 
 from javis.config.settings import ConfigurationError, Settings
@@ -32,6 +34,13 @@ def run_gui(argv: Sequence[str] | None = None) -> int:
         return 2
     window = MainWindow(DesktopController(runtime), approval_bridge)
     window.show()
+    smoke_exit = os.environ.get("JAVIS_GUI_SMOKE_EXIT_MS")
+    if smoke_exit:
+        try:
+            delay = max(1, min(int(smoke_exit), 10_000))
+        except ValueError:
+            delay = 500
+        QTimer.singleShot(delay, application.quit)
     return application.exec()