feat: mousearea, datetime dates, dir(), renpy.image_size and style.rebuild for Ren'Py games

Screens get an invisible mousearea that reports the pointer entering and leaving without taking
clicks. datetime.date/datetime/timedelta support construction and date arithmetic. dir() lists the
game's variables, renpy.style.rebuild() is a no-op, and renpy.image_size answers only for pictures
the browser already holds (otherwise an IOError the game can catch).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

backend/app/converter/compatibility.py

@@ -120,6 +120,8 @@ CALLS |= {"renpy.start_predict", "renpy.stop_predict", "renpy.start_predict_scre
           "renpy.ui.imagebutton", "renpy.return_statement"}
 from app.games.renpy_native import NATIVE_CLASSES, NATIVE_METHODS  # noqa: E402
 CALLS |= set(NATIVE_CLASSES)
+CALLS |= {"dir", "datetime.date", "datetime.datetime", "datetime.timedelta", "date", "timedelta",
+          "renpy.style.rebuild", "renpy.image_size"}
 CALLS |= {"map", "filter", "iter", "hash", "hasattr", "getattr", "setattr", "callable", "super"}
 # Screen actions and values the player implements (see frontend/src/player/screens.ts)
 SCREEN_CALLS = set("""Jump Call Return SetVariable ToggleVariable SetDict SetField ToggleField