Add consistent > prompt for IF mode in server loop

src/mudlib/server.py

@@ -315,8 +315,7 @@ async def shell(
             if player.mode == "editor" and player.editor:
                 _writer.write(f"  {player.editor.cursor + 1}> ")
             elif player.mode == "if" and player.if_session:
-                # IF mode: game writes its own prompt, don't add another
-                pass
+                _writer.write("> ")
             else:
                 _writer.write("mud> ")
             await _writer.drain()