feat: improve RenPy conversion and support MIST runtime

backend/tests/test_compatibility.py

@@ -80,7 +80,7 @@ def test_renpy_only_declarations_are_not_execution_blockers(tmp_path):
 
 
 @pytest.mark.parametrize("source,reason", [
-    ('init python:\n    def helper():\n        yield 1\nlabel start:\n    "Hi"', "init python"),
+    ('init python:\n    def helper():\n        yield 1\nlabel start:\n    $ helper()', "init python"),
     ('label start:\n    $ result = renpy.show_displayable("map")', "renpy.show_displayable"),
     ('label start:\n    jump missing', "missing"),
 ])