feat: Ren'Py screens (screen/call screen/show screen) with actions and styles

Converter
- screens.py parses the screen language: containers (fixed, frame, vbox, hbox,
  grid, vpgrid, viewport, button, has), widgets (text, textbutton, imagebutton,
  add, bar ...), if/for/use/transclude, default, python, key, timer, on, inline ATL,
  conditional properties, and decompiled forms (unparenthesised operators,
  glued property values, comma separated actions)
- style statements, call/show/hide screen operators and Python-level
  renpy.show_screen are translated; only screens the game shows are audited,
  unused stock screens no longer block an import; undefined screens do
- ATL values may be computed at run time and transforms take parameters
  (at blink(0.2, 0.3)); blur property

Player
- screens.ts builds the DOM from the IR and rebuilds it on state changes;
  buttons with idle/hover/selected/insensitive states, tooltips, sounds, modal
  screens, timers and keys that survive re-rendering, saved with the save file
- Actions: Jump, Call, Return, SetVariable, Toggle*, SetScreenVariable, Show, Hide,
  ToggleScreen, Function, Play, Notify, If, Language, ShowMenu, OpenURL ...
- Crop/LiveCrop/Solid/Frame/Transform/DynamicDisplayable values, crop property,
  globals(), renpy.variant/change_language/seen_image, transition stubs

Tests: screen parser and runtime (linkedom DOM), screens fixture compiled from
tests/fixtures/screens.rpy. Docs: docs/SCREENS.md.

Twisted-Thoughts now passes the strict compatibility check.

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

backend/app/converter/pipeline.py

@@ -191,6 +191,8 @@ def convert_archive(archive: Path, filename: str, work: Path, progress: Progress
         "images": images,
         "transforms": data.transforms,
         "atl": data.atl,
+        "screens": {name: data.screens[name] for name in sorted(_used_screens(data))},
+        "styles": data.styles,
         "transitions": data.transitions,
         "audio": audio,
         "channels": data.channels,
@@ -297,6 +299,20 @@ def _size(path: Path) -> int:
 ENGINE_DIRS = ("cache", "saves", "tl", "renpy", "0x52-urm")
 
 
+def _used_screens(data: ScriptData) -> set[str]:
+    """Screens the game shows (and the ones those open); the rest stay out of game.json."""
+    from app.converter.screens import referenced_screens
+
+    used = {name for name in data.screen_used if name in data.screens}
+    pending = list(used)
+    while pending:
+        for other in referenced_screens(data.screens[pending.pop()], data.screens):
+            if other not in used:
+                used.add(other)
+                pending.append(other)
+    return used
+
+
 def _is_engine_file(game_dir: Path, p: Path) -> bool:
     parts = [x.lower() for x in p.relative_to(game_dir).parts]
     return len(parts) > 1 and parts[0] in ENGINE_DIRS