SQ -> Shell: Fix race condition where shell might start accepting com…

…mands before foreground thread created

src/crystal/main.py

@@ -286,15 +286,16 @@ def _finish_launch(self, filepath: Optional[str]=None) -> None:
     from crystal.util.xthreading import is_quitting, set_foreground_thread
     set_foreground_thread(threading.current_thread())
     try:
+        # (Don't insert anything between set_foreground_thread() and MyApp())
+        app = MyApp(redirect=False)
+
         # Start shell if requested
         if parsed_args.shell:
             from crystal.shell import Shell
             shell = Shell()
         else:
             shell = None
 
-        app = MyApp(redirect=False)
-
         # Starts tests if requested
         if parsed_args.test is not None:
             from crystal.util.xthreading import bg_call_later, fg_call_later, has_foreground_thread