feat: generator interpreter for Python that waits for the player (Ren'Py)

Python containing renpy.input, narrator("..."), character calls, renpy.say,
renpy.pause, renpy.display_menu, renpy.with_statement or renpy.call_screen now
runs through loops, try, functions, methods and expressions.

Player
- python.ts: execG/evalG/callG run only the code that may wait (mayBlock);
  everything else stays on the synchronous fast path. A waiting call returns a
  BlockingCall; outside the generator interpreter it is an explicit error. The
  interpreter scope is set aside while the player decides
- engine: drives the generator and answers requests (dialogue, text input with
  length/allow/exclude, pause, choice menu, transition, call screen)
- renpy.show/hide/scene, transitions and transforms as Python values,
  Character(...) objects, Borders, set_tag_attributes

Converter
- blocking_names() lists game functions that may wait, transitively, and ships
  them as game.json "blocking"; character calls are allowed
- hide screen of an unknown screen is harmless; images defined by a parenthesised
  expression are supported

Hooked now passes the strict compatibility check (with Tomie and Twisted-Thoughts).
Tests: waiting.py fixture run through the generator interpreter; blocking-name analysis.

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

frontend/tests/fixtures/waiting.py

@@ -0,0 +1,36 @@
+# Source of waiting.ir.json (Python that waits for the player through ask()). Regenerate from backend/ with:
+#   python -m tests.make_ir ../frontend/tests/fixtures/waiting.py ../frontend/tests/fixtures/waiting.ir.json
+
+
+def greet(n):
+    name = ask("name?")
+    while len(name) < 2:
+        name = ask("again")
+    return "hi " + name
+
+
+def helper(k):
+    total = 0
+    for i in range(k):
+        try:
+            v = ask("v")
+            total += int(v)
+        except ValueError:
+            continue
+    return total
+
+
+class Q(object):
+    def __init__(self):
+        self.v = ask("init")
+
+    def twice(self):
+        return ask("x") + ask("y")
+
+
+result = greet(1) + "!"
+t = helper(3)
+q = Q()
+r2 = q.twice()
+cond = "a" if ask("c") == "yes" else "b"
+plain = len("abc") + 1