refactor(app_controller): migrate _cb_run_conductor_setup + _cb_load_track to Result (Phase 6 Groups 6.5+6.7 partial)

Migrates the 2 remaining _cb_* sites with proper Result[T] propagation:
- _cb_run_conductor_setup: per-file read via _read_conductor_file_result
- _cb_load_track: state hydration via _cb_load_track_result

New helpers:
- _read_conductor_file_result(f) -> Result[int]
- _cb_load_track_result(state, track_id) -> Result[None]

Audit: INTERNAL_SILENT_SWALLOW for src/app_controller.py: 12 -> 10.

src/app_controller.py

@@ -4749,6 +4749,22 @@ class AppController:
      engine.engine = ExecutionEngine(engine.dag, auto_queue=engine.engine.auto_queue)
    self._push_mma_state_update()
 
+ def _read_conductor_file_result(self, f: Path) -> "Result[int]":
+  """Phase 6 Group 6.7: read a conductor file and return line count.
+  On failure: OSError/IOError/UnicodeDecodeError -> ErrorInfo(original=e).
+  Caller (`_cb_run_conductor_setup`) records per-file errors and
+  adds an 'Error reading' line to the summary."""
+  try:
+   with open(f, "r", encoding="utf-8") as fd:
+    return Result(data=len(fd.readlines()))
+  except (OSError, IOError, UnicodeDecodeError) as e:
+   return Result(data=0, errors=[ErrorInfo(
+    kind=ErrorKind.INTERNAL,
+    message=str(e),
+    source=f"app_controller._read_conductor_file_result[{f.name}]",
+    original=e,
+   )])
+
  def _cb_run_conductor_setup(self) -> None:
   """
     [C: src/gui_2.py:App._render_mma_conductor_setup, tests/test_gui_phase3.py:test_conductor_setup_scan]
@@ -4763,13 +4779,12 @@ class AppController:
   summary.append(f"Total Files: {len(files)}")
   total_lines = 0
   for f in files:
-   try:
-    with open(f, "r", encoding="utf-8") as fd:
-     lines = len(fd.readlines())
-     total_lines += lines
-     summary.append(f"- {f.relative_to(base)}: {lines} lines")
-   except (OSError, IOError, UnicodeDecodeError) as e:
-    logging.getLogger(__name__).debug("conductor file read failed for %s: %s", f, e, extra={"source": "app_controller._cb_run_conductor_setup"})
+   result = self._read_conductor_file_result(f)
+   if result.ok:
+    total_lines += result.data
+    summary.append(f"- {f.relative_to(base)}: {result.data} lines")
+   else:
+    self._last_request_errors.append((f"conductor_file_read[{f.name}]", result.errors[0]))
     summary.append(f"- {f.relative_to(base)}: Error reading")
   summary.append(f"Total Line Count: {total_lines}")
   tracks_dir = base / "tracks"
@@ -4842,34 +4857,49 @@ class AppController:
   """
   state = project_manager.load_track_state(track_id, self.active_project_root)
   if state:
-   try:
+   result = self._cb_load_track_result(state, track_id)
+   if not result.ok:
+    err = result.errors[0]
+    self.ai_status = f"Load track error: {err.message}"
+    print(f"Error loading track {track_id}: {err.message}")
+    self._report_worker_error("cb_load_track", result)
+
+ def _cb_load_track_result(self, state, track_id: str) -> "Result[None]":
+  """Phase 6 Group 6.7: load a track with Result propagation.
+  On failure: OSError/IOError/ValueError/TypeError/KeyError/AttributeError/tomllib.TOMLDecodeError
+  -> ErrorInfo(original=e). Caller drains via stderr print + ai_status."""
+  try:
    # Convert list[Ticket] or list[dict] to list[Ticket] for Track object
-    tickets = []
-    for t in state.tasks:
-     if isinstance(t, dict):
-      tickets.append(models.Ticket(**t))
-     else:
-      tickets.append(t)
-    self.active_track = models.Track(
-     id=state.metadata.id,
-     description=state.metadata.name,
-     tickets=tickets
-    )
-    # Keep dicts for UI table
-    self._load_active_tickets()
-    # Load track-scoped history
-    history = project_manager.load_track_history(track_id, self.active_project_root)
-    with self._disc_entries_lock:
-     if history:
-      self.disc_entries[:] = models.parse_history_entries(history, self.disc_roles)
-     else:
-      self.disc_entries.clear()
-    self._recalculate_session_usage()
-    self.ai_status = f"Loaded track: {state.metadata.name}"
-   except (OSError, IOError, ValueError, TypeError, KeyError, AttributeError, tomllib.TOMLDecodeError) as e:
-    logging.getLogger(__name__).debug("load track failed: %s", e, extra={"source": "app_controller._cb_load_track"})
-    self.ai_status = f"Load track error: {e}"
-    print(f"Error loading track {track_id}: {e}")
+   tickets = []
+   for t in state.tasks:
+    if isinstance(t, dict):
+     tickets.append(models.Ticket(**t))
+    else:
+     tickets.append(t)
+   self.active_track = models.Track(
+    id=state.metadata.id,
+    description=state.metadata.name,
+    tickets=tickets
+   )
+   # Keep dicts for UI table
+   self._load_active_tickets()
+   # Load track-scoped history
+   history = project_manager.load_track_history(track_id, self.active_project_root)
+   with self._disc_entries_lock:
+    if history:
+     self.disc_entries[:] = models.parse_history_entries(history, self.disc_roles)
+    else:
+     self.disc_entries.clear()
+   self._recalculate_session_usage()
+   self.ai_status = f"Loaded track: {state.metadata.name}"
+   return OK
+  except (OSError, IOError, ValueError, TypeError, KeyError, AttributeError, tomllib.TOMLDecodeError) as e:
+   return Result(data=None, errors=[ErrorInfo(
+    kind=ErrorKind.INTERNAL,
+    message=str(e),
+    source="app_controller._cb_load_track_result",
+    original=e,
+   )])
 
  def _push_mma_state_update(self) -> None:
   """