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/mods.py

@@ -14,6 +14,7 @@ from app.translation import file_json, put_json
 OPS = set("label camera say scene show hide with play stop queue voice pause menu if while jump call return exec window noop nvl".split())
 OPS |= {"nani_add_choice", "nani_menu", "nani_clear_choice", "nani_hide_characters", "nani_exit"}
 OPS.add("nani_command")
+OPS |= {"call_screen", "show_screen", "hide_screen"}
 MISSING = object()
 
 
@@ -77,6 +78,13 @@ def validate(doc, manifest):
             for key in ("expr", "c", "d"):
                 if isinstance(n.get(key), dict):
                     expression(n[key])
+            if op in ("call_screen", "show_screen"):
+                if not isinstance(n.get("name"), str) or not isinstance(n.get("args"), list):
+                    raise ValueError("Некорректный вызов screen")
+                for item in [*n["args"], *(n.get("kw") or {}).values()]:
+                    expression(item)
+            if op == "hide_screen" and not isinstance(n.get("name"), str):
+                raise ValueError("Некорректный вызов screen")
             if op in {"say", "nani_add_choice"} or (op == "nani_command" and "what" in n):
                 if not isinstance(n.get("what"), str) or not isinstance(n.get("tid"), str) or n["tid"] in tids:
                     raise ValueError("Некорректная реплика или повторяющийся tid")