feat: ATL pictures/contains/function/time, colour matrices and more Python for Ren'Py

ATL
- Image blocks become timelines: picture steps with dissolve, parallel, contains,
  finite repeat, time, function f(trans, st, at), calls of other transforms with
  arguments, on hover/idle events for buttons. Animations stop when their element
  leaves the page
- Pictures defined by an expression (get_face_path("base")) are drawn at show time
- Purely graphical hints (shader, mesh, gl_*, u_*) are accepted and dropped

Colour
- matrixcolor and im.matrix.* as 5x5 matrices combined with `*`, applied through SVG
  filters; im.MatrixColor/Scale/Crop/Blur/Composite and Text/Image as values

Python
- match statement, re/copy/time/datetime/defaultdict/functools.partial, more
  str/dict methods, Character(...) created by code
- narrator("..."), Character calls, renpy.say and renpy.show/hide with expressions in
  Python blocks become script nodes
- Audit follows reachability: functions and classes nothing refers to (custom
  statement lexers, unused tools) no longer block an import

Docs: README and ARCHITECTURE now describe a multi-engine library (GameMaker and
QSP planned). Tests for the new runtime pieces.

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

backend/app/converter/screens.py

@@ -21,6 +21,7 @@ from typing import Any
 
 from app.converter import pyexpr
 from app.converter.atl import WARPER
+from app.converter.exprtokens import read_value
 from app.converter.pyexpr import Unsupported
 from app.converter.rpy_lexer import Line
 
@@ -41,7 +42,7 @@ ymargin left_margin right_margin top_margin bottom_margin width height""".split(
 LOOK = set("""background foreground idle hover insensitive selected selected_idle selected_hover
 selected_insensitive auto ground left_bar right_bar top_bar bottom_bar thumb alpha zoom rotate xzoom yzoom
 clipping fit_first xfit yfit box_reverse box_wrap order_reverse transpose rows cols crop size_group
-xtile ytile""".split())
+xtile ytile matrixcolor blur""".split())
 TEXT = set("""color size font bold italic underline strikethrough outlines text_align textalign line_spacing
 kerning layout first_indent min_width antialias xalign yalign justify hyperlink_functions slow_cps""".split())
 BEHAVIOUR = set("""action alternate hovered unhovered sensitive tooltip focus_mask mouse hover_sound
@@ -58,8 +59,6 @@ STATE_PREFIXES = ("idle", "hover", "insensitive", "selected", "selected_idle", "
 ALL = LAYOUT | LOOK | TEXT | BEHAVIOUR
 SCREEN_PROPS = {"zorder", "modal", "tag", "variant", "style_prefix", "layer", "sensitive", "style"}
 DESKTOP_VARIANTS = {"pc", "large", "web", "medium", "small"}
-OPERATORS = {"+", "-", "*", "/", "//", "%", "**", "==", "!=", "<", ">", "<=", ">=", "and", "or", "in", "is",
-             "if", "else", "not"}
 GLUED = re.compile(r"^([a-z_][a-z_0-9]*)(\(.*\)|\[.*\])$", re.S)
 
 
@@ -110,29 +109,6 @@ def tokens(text: str) -> list[str]:
     return out
 
 
-def read_value(words: list[str], i: int) -> tuple[str, int]:
-    """One property value starting at words[i]. Decompiled sources keep operators unparenthesised
-    (``text "Day " + str(day)``), so a value continues while the next word is an operator."""
-    parts = [words[i]]
-    i += 1
-    if parts[0] in ("not", "-") and i < len(words):
-        parts.append(words[i])
-        i += 1
-    while i < len(words):
-        if words[i].startswith("(") and re.search(r"[\w\])]$", parts[-1]):  # `ToggleVariable ("x")`
-            parts[-1] += words[i]
-            i += 1
-        elif parts[-1].endswith(",") or parts[-1] in OPERATORS:  # `A(), B()` / `a +` continue with the next word
-            parts.append(words[i])
-            i += 1
-        elif i + 1 < len(words) and words[i] in OPERATORS:
-            parts.extend([words[i], words[i + 1]])
-            i += 2
-        else:
-            break
-    return " ".join(parts), i
-
-
 class ScreenParser:
     def __init__(self, warn: Callable[[str, Line], None], transform_ref: Callable[[str, Line], dict],
                  atl: Callable[[list[Line]], tuple[dict, dict | None]] | None = None):
@@ -191,7 +167,8 @@ class ScreenParser:
         i = 0
         while i < len(lines):
             line = lines[i]
-            words = tokens(line.text.rstrip(":").strip() if line.block else line.text.strip())
+            text = line.text.rstrip(":").strip() if line.block else line.text.strip()
+            words = tokens(re.sub(r"^(if|elif|showif)\(", r"\1 (", text))
             i += 1
             if not words:
                 continue
@@ -199,7 +176,7 @@ class ScreenParser:
             if first in ("if", "showif"):
                 branches = [self.branch(first, words, line)]
                 while i < len(lines):
-                    nxt = tokens(lines[i].text.rstrip(":").strip())
+                    nxt = tokens(re.sub(r"^(elif|else)\(", r"\1 (", lines[i].text.rstrip(":").strip()))
                     if not nxt or nxt[0] not in ("elif", "else"):
                         break
                     branches.append(self.branch(nxt[0], nxt, lines[i]))