refactor(config): Route all config I/O through AppController

Eliminates 22 call sites that bypassed the AppController state owner
and read/wrote config.toml directly. AppController is now the single
source of truth for self.config; gui_2.py, commands.py, etc. go
through controller.save_config() / controller.load_config().

Production changes:
- src/models.py: rename load_config -> _load_config_from_disk,
  save_config -> _save_config_to_disk (private I/O primitives)
- src/app_controller.py: add public load_config()/save_config() methods
  that own the state. Update 3 internal call sites and 3 ConductorEngine
  call sites to pass max_workers from self.config
- src/multi_agent_conductor.py: ConductorEngine.__init__ now takes
  max_workers as a parameter (caller responsibility, not I/O primitive)
- src/external_editor.py: get_default_launcher() takes config as a
  parameter; gui_2.py:1311,4776 pass app.config
- src/gui_2.py: 17 sites of models.save_config(X.config) replaced with
  X.save_config() (delegates via __getattr__ to controller)
- src/commands.py: save_all() uses app.save_config()

Test changes (route through controller, not I/O primitive):
- tests/conftest.py: mock_app and app_instance fixtures now patch
  AppController.load_config/save_config instead of models I/O primitives
- 18 other test files: patches renamed from models._save_config_to_disk
  to AppController.save_config (and same for load_config)
- tests/test_app_controller_mcp.py: use SLOP_CONFIG env var instead of
  patching removed CONFIG_PATH module constant
- tests/test_parallel_execution.py: pass max_workers=2 explicitly to
  ConductorEngine (caller no longer reads config)
- tests/test_gui_paths.py: add save_config=MagicMock() to MockApp;
  assert on controller method, not I/O primitive
- tests/test_models_no_top_level_tomli_w.py: still calls private
  _save_config_to_disk directly (the only allowed exception; tests
  the lazy-load behavior of the primitive itself)

New files:
- scripts/audit_no_models_config_io.py: enforces the rule (--strict,
  --json modes; AST-based docstring detection to avoid false positives)
- conductor/code_styleguides/config_state_owner.md: documents the rule

Verification:
- 67 targeted tests pass
- scripts/audit_no_models_config_io.py --strict returns 0

This is the architectural cleanup that surfaced during the
audit_architectural_cheats_20260607 review. Closes the smoke-gun
CONFIG_PATH module constant (already done in 0c7ebf22) AND the
free-function models.load_config/save_config smell.

[conductor(checkpoint): config-iO-refactor-20260607]

src/app_controller.py

@@ -1707,7 +1707,7 @@ class AppController:
   self.ui_separate_response_panel   = False
   self.ui_separate_tool_calls_panel = False
   self.ui_separate_external_tools   = False
-  self.config = models.load_config()
+  self.config = self.load_config()
   theme.load_from_config(self.config)
   ai_cfg = self.config.get("ai", {})
   self._current_provider   = ai_cfg.get("provider", "gemini")
@@ -2685,7 +2685,7 @@ class AppController:
  def _cb_project_save(self) -> None:
   self._flush_to_project()
   self._flush_to_config()
-  models.save_config(self.config)
+  self.save_config()
   self.ai_status = "config saved"
 
  def _do_project_switch(self, path: str) -> None:
@@ -3360,7 +3360,7 @@ class AppController:
   """
   self._flush_to_project()
   self._flush_to_config()
-  models.save_config(self.config)
+  self.save_config()
   track_id = self.active_track.id if self.active_track else None
   flat = project_manager.flat_config(self.project, self.active_discussion, track_id=track_id)
   
@@ -3997,7 +3997,9 @@ class AppController:
    if self.active_track and self.active_track.id == track_id:
    # Use the active track object directly to start execution
     self.mma_status = "running"
-    engine = multi_agent_conductor.ConductorEngine(self.active_track, self.event_queue, auto_queue=not self.mma_step_mode)
+    _mma_cfg = self.config.get("mma", {})
+    _max_workers = int(_mma_cfg.get("max_workers", 4))
+    engine = multi_agent_conductor.ConductorEngine(self.active_track, self.event_queue, auto_queue=not self.mma_step_mode, max_workers=_max_workers)
     self.engines[self.active_track.id] = engine
     flat = project_manager.flat_config(self.project, self.active_discussion, track_id=self.active_track.id)
     full_md, _, _ = aggregate.run(flat)
@@ -4008,7 +4010,9 @@ class AppController:
     self._cb_load_track(track_id)
     if self.active_track and self.active_track.id == track_id:
      self.mma_status = "running"
-     engine = multi_agent_conductor.ConductorEngine(self.active_track, self.event_queue, auto_queue=not self.mma_step_mode)
+     _mma_cfg = self.config.get("mma", {})
+     _max_workers = int(_mma_cfg.get("max_workers", 4))
+     engine = multi_agent_conductor.ConductorEngine(self.active_track, self.event_queue, auto_queue=not self.mma_step_mode, max_workers=_max_workers)
      self.engines[self.active_track.id] = engine
      flat = project_manager.flat_config(self.project, self.active_discussion, track_id=self.active_track.id)
      full_md, _, _ = aggregate.run(flat)
@@ -4084,7 +4088,9 @@ class AppController:
    # 4. Initialize ConductorEngine and run loop
    sys.stderr.write(f"[DEBUG] _start_track_logic: Initializing engine for {track_id}...\n")
    sys.stderr.flush()
-   engine = multi_agent_conductor.ConductorEngine(track, self.event_queue, auto_queue=not self.mma_step_mode)
+   _mma_cfg = self.config.get("mma", {})
+   _max_workers = int(_mma_cfg.get("max_workers", 4))
+   engine = multi_agent_conductor.ConductorEngine(track, self.event_queue, auto_queue=not self.mma_step_mode, max_workers=_max_workers)
    self.engines[track.id] = engine
    # Use current full markdown context for the track execution
    track_id_param = track.id
@@ -4369,6 +4375,32 @@ class AppController:
     except Exception as e:
      print(f"Error loading beads: {e}")
 
+ #region: --- Config I/O (single source of truth) ---
+ def load_config(self) -> Dict[str, Any]:
+  """
+  Re-read the global config.toml from disk and update self.config.
+  Returns the dict (also stored in self.config). Single source of
+  truth for the in-memory config is self.config. Direct callers
+  from outside the controller (e.g. models.load_config) are an
+  architectural smell and will be flagged by
+  scripts/audit_no_models_config_io.py.
+  [C: src/app_controller.py:AppController.__init__]
+  """
+  self.config = models._load_config_from_disk()
+  return self.config
+
+ def save_config(self) -> None:
+  """
+  Flush self.config to disk. Single source of truth = self.config.
+  This method owns the write path. Direct callers from outside the
+  controller (e.g. models.save_config) are an architectural smell
+  and will be flagged by
+  scripts/audit_no_models_config_io.py.
+  [C: src/app_controller.py:AppController._cb_project_save, src/app_controller.py:AppController._do_generate]
+  """
+  models._save_config_to_disk(self.config)
+ #endregion: --- Config I/O (single source of truth) ---
+
  #endregion: MMA (Controller)
 
 #region: MMA