feat: eval/exec of strings, gallery Replay, callable actions; iNSight and SomethingBetter now pass

- pyparse.ts: parser for expressions and simple statements built at run time, producing
  the sandbox's own IR; backs eval() and exec() (e.g. exec("persistent." + var + " = 0"))
- Replay/EndReplay and renpy.end_replay: the engine stashes the full game state, runs the
  label with the given scope and restores everything when it ends; locked replays are
  insensitive. Save loading shared as applySave()
- Screen actions are callable (MainMenu(confirm=False)())
- jump main_menu_screen is Ren'Py's own label: it opens the player's main menu
- Screens: a closing quote ends the word before a letter ("text"size 15) but not before
  an operator ("a"+b); Text(...) pictures in image blocks
- README: current capabilities and limits of the Ren'Py support

Strict compatibility check on the local collection: Tomie, Twisted-Thoughts, Hooked,
iNSight-of-you and SomethingBetter pass; TheFixer (custom AlphaMask wardrobe, missing
labels) and That_New_Teacher (custom statements, Render API) do not.

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

backend/tests/test_screens.py

@@ -159,3 +159,13 @@ def test_computed_atl_values_make_a_transform_animated():
     assert block["params"][0]["n"] == "x"
     assert block["steps"][0]["props"]["xoffset"] == {"e": {"k": "name", "id": "x"}}
     assert data.transforms["shift"] == {}
+
+
+def test_a_closing_quote_ends_the_word_and_text_pictures_are_understood():
+    data = parse(
+        'screen hud():\n    text "D [a] A [b]"size 15\n    text "x" size 20\n'
+        'image log_line:\n    Text(log.message())\n    alpha 0.0\n    linear 0.5 alpha 1.0\n'
+        'label start:\n    call screen hud\n')
+    first = data.screens["hud"]["body"][0]
+    assert first["props"]["size"] == {"k": "const", "v": 15}
+    assert data.images["log_line"]["textExpr"]["k"] == "call"