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/tests/test_screens.py

@@ -79,10 +79,10 @@ def test_screens_styles_and_calls_become_ir():
 
 
 def test_shown_screens_are_audited_but_unshown_ones_are_not():
-    data = parse('screen odd():\n    mousearea:\n        pass\nlabel start:\n    "Hi"\n')
+    data = parse('screen odd():\n    frobnicate:\n        pass\nlabel start:\n    "Hi"\n')
     audit_ir(data)
     require_supported_scripts(data)  # never shown: harmless
-    data = parse('screen odd():\n    mousearea:\n        pass\nlabel start:\n    call screen odd\n')
+    data = parse('screen odd():\n    frobnicate:\n        pass\nlabel start:\n    call screen odd\n')
     audit_ir(data)
     with pytest.raises(CompatibilityError, match="screen"):
         require_supported_scripts(data)
@@ -169,3 +169,12 @@ def test_a_closing_quote_ends_the_word_and_text_pictures_are_understood():
     first = data.screens["hud"]["body"][0]
     assert first["props"]["size"] == {"k": "const", "v": 15}
     assert data.images["log_line"]["textExpr"]["k"] == "call"
+
+
+def test_mousearea_is_a_leaf_with_hover_actions():
+    data = parse('screen s():\n    mousearea:\n        xysize (100, 50)\n        hovered SetVariable("h", True)\n'
+                 '        unhovered SetVariable("h", False)\nlabel start:\n    call screen s\n')
+    audit_ir(data)
+    require_supported_scripts(data)
+    node = data.screens["s"]["body"][0]
+    assert node["w"] == "mousearea" and {"hovered", "unhovered", "xysize"} <= set(node["props"])