TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 10: refactor(gui_2): migrate L1693 render_main_interface autosave to Result[T] (Phase 10 site 9)

Extracted _autosave_flush_result(app) -> Result[None] helper above the
call site in render_main_interface.
ANTI-SLIMING: full Result[T] propagation (NO except+pass with comment).
The helper returns Result(data=None) on success or Result(data=None,
errors=[ErrorInfo]) on exception (logging NOT a drain per the user's
principle 2026-06-17). The 'don't disrupt the GUI loop' intent is
preserved via the data plane (app._last_request_errors) rather than
silent swallow.

The legacy render_main_interface code preserves its behavior, calls the
helper, and drains errors to app._last_request_errors.

Tests: 2 new tests verify both paths (success and OSError).

Audit: L1693 reclassified from INTERNAL_SILENT_SWALLOW (5 sites remaining,
was 6). New helper L1693 is INTERNAL_COMPLIANT.

tests/test_gui_2_result.py

@@ -2068,4 +2068,47 @@ def test_phase_10_l1647_focus_response_window_result_failure():
  assert "IM_ASSERT" in err.message
 
 
+def test_phase_10_l1693_autosave_flush_result_success():
+ """
+ L1693 _autosave_flush_result returns Result(data=None) on success.
+
+ The helper extracts the auto-save flush_to_project + flush_to_config +
+ save_config try/except from render_main_interface into a Result-returning
+ helper. On success, returns Result(data=None). The legacy wrapper
+ continues with the GUI loop.
+ """
+ from unittest.mock import MagicMock
+ import src.gui_2 as gui2_mod
+ app = MagicMock()
+ result = gui2_mod._autosave_flush_result(app)
+ assert result.ok, f"Expected ok=True on success, got errors: {result.errors}"
+ assert result.data is None
+ app._flush_to_project.assert_called_once()
+ app._flush_to_config.assert_called_once()
+ app.save_config.assert_called_once()
+
+
+def test_phase_10_l1693_autosave_flush_result_failure():
+ """
+ L1693 _autosave_flush_result returns Result(data=None, errors=[ErrorInfo]) on failure.
+
+ When any of _flush_to_project/_flush_to_config/save_config raises
+ (disk full, JSON parse error), the helper converts to ErrorInfo. The
+ caller (render_main_interface) drains to self._last_request_errors and
+ continues with the GUI loop (preserving the original "don't disrupt the
+ GUI loop" intent via the data plane rather than silent swallow).
+ """
+ from unittest.mock import MagicMock
+ import src.gui_2 as gui2_mod
+ app = MagicMock()
+ app._flush_to_project.side_effect = OSError("disk full")
+ result = gui2_mod._autosave_flush_result(app)
+ assert not result.ok, f"Expected ok=False on failure, got data: {result.data}"
+ assert result.data is None
+ assert result.errors, "Expected at least one error on failure"
+ err = result.errors[0]
+ assert err.source == "gui_2._autosave_flush_result"
+ assert "disk full" in err.message
+
+