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>

backend/tests/test_converter.py

@@ -195,3 +195,24 @@ def test_gui_variants_and_renpy_store_are_understood():
     assert d.init_code[0]["decos"] == [] and d.init_code[0]["name"] == "twice"
     assert d.init_code[1]["e"]["f"]["o"] == {"k": "name", "id": "seen"}
     assert not d.blockers
+
+
+def test_functions_that_wait_for_the_player_are_listed_transitively():
+    from app.converter.compatibility import audit_ir, blocking_names
+
+    d = parse(
+        "define e = Character('E')\n"
+        "init python:\n"
+        "    def ask_name():\n"
+        "        return renpy.input('Name?')\n"
+        "    def outer():\n"
+        "        n = ask_name()\n"
+        "        e('hi ' + n)\n"
+        "    def plain(x):\n"
+        "        return x + 1\n"
+        "label start:\n"
+        "    $ outer()\n"
+        "    $ y = plain(2)\n")
+    audit_ir(d)
+    assert not d.blockers
+    assert blocking_names(d) == ["ask_name", "outer"]