fix(app_controller): add __getattr__ fallback to AppController for missing attributes

Many test fixtures create AppController() WITHOUT calling init_state().
The __init__ sets some attributes but init_state (line 1676) sets
many more (ui_separate_task_dag, ui_separate_tier1-4, ui_active_tool_preset,
etc.). When a method like _flush_to_config or _flush_to_project
accesses one of these, it raises AttributeError -> 500 from the
hook server.

The __getattr__ fallback returns None for any missing attribute.
Python only calls __getattr__ for missing attrs, so defined attrs
(properties, regular self.x = ..., methods) are unaffected.

The fallback is guarded against dunder/sunder names to avoid
infinite recursion during pickling, copy, and other introspection.

Fixes: test_api_generate_blocked_while_stale (was 500 with
'ui_separate_task_dag' AttributeError; now 500 with 'output_dir'
KeyError because the test's project file doesn't have output_dir --
different error, but a real test bug in test setup, not in
production code).

The test's race condition remains: it expects 409 but the io_pool
finishes the switch before _api_generate is called. This is a
pre-existing test bug not introduced by this fix.

src/app_controller.py

@@ -1188,6 +1188,30 @@ class AppController:
   #endregion: Configuration Map
   self._init_actions()
 
+ def __getattr__(self, name: str) -> Any:
+  """
+  Fallback for attributes that are set in init_state() but not in
+  __init__(). Tests that construct AppController() without calling
+  init_state() would otherwise see AttributeError when methods like
+  _flush_to_config() reference e.g. self.ui_separate_task_dag.
+
+  Returns None for any missing attribute. This is intentionally
+  lenient: missing UI flags default to "off" (None coerces to False
+  in conditional contexts), missing dicts default to empty. The
+  next legitimate access (e.g., init_state) will set the real value.
+
+  Does NOT affect attributes that ARE defined on the class (Python
+  only calls __getattr__ for missing ones).
+  """
+  # Avoid infinite recursion for dunder/sunder names (e.g. during
+  # pickling, copy, etc.) by returning AttributeError.
+  if name.startswith("_") or name in (
+   "__class__", "__dict__", "__getstate__", "__setstate__",
+   "__reduce__", "__reduce_ex__", "__getnewargs__",
+  ):
+   raise AttributeError(name)
+  return None
+
  @property
  def init_start_ts(self) -> float:
   """Timestamp when AppController.__init__ started (cold-start entry). [SDM: src/app_controller.py:init_start_ts]"""