TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 5: refactor(gui_2): migrate L5380 render_operations_hub ext_editor_panel to Result[T] (Phase 5)

Extract _render_operations_hub_external_editor_panel_result helper from the
render_external_editor_panel call try/except in render_operations_hub
External Tools tab. Legacy wrapper drains errors to app._last_request_errors
per FR-BC-4 event-handler pattern.

[pre-audit] L5380 INTERNAL_BROAD_CATCH
[post-audit] V count: 7 -> 6 (L5380 removed)

tests/test_gui_2_result.py

@@ -1107,3 +1107,38 @@ def test_phase_5_l3582_render_context_batch_actions_preview_result_failure():
  assert err.source == "gui_2._render_context_batch_actions_preview_result"
  assert "generate failed" in err.message
  assert "Error" in result.data
+
+
+def test_phase_5_l5380_render_operations_hub_external_editor_panel_result_success():
+ """
+ L5380 _render_operations_hub_external_editor_panel_result returns Result.ok=True on success.
+
+ The helper wraps the render_external_editor_panel call within render_operations_hub
+ External Tools tab try/except. On success, returns Result(data=True).
+ """
+ from src import gui_2
+ from unittest.mock import MagicMock, patch
+ app = MagicMock()
+ with patch.object(gui_2, "render_external_editor_panel"):
+  result = gui_2._render_operations_hub_external_editor_panel_result(app)
+ assert result.ok, f"Expected ok=True on success, got errors: {result.errors}"
+ assert result.data is True
+
+
+def test_phase_5_l5380_render_operations_hub_external_editor_panel_result_failure():
+ """
+ L5380 _render_operations_hub_external_editor_panel_result returns Result.ok=False on failure.
+
+ When render_external_editor_panel raises, the helper converts the exception
+ to ErrorInfo and returns Result(data=False, errors=[ErrorInfo]).
+ """
+ from src import gui_2
+ from unittest.mock import MagicMock, patch
+ app = MagicMock()
+ with patch.object(gui_2, "render_external_editor_panel", side_effect=RuntimeError("ext editor render blew up")):
+  result = gui_2._render_operations_hub_external_editor_panel_result(app)
+ assert not result.ok, f"Expected ok=False on failure, got data: {result.data}"
+ assert result.errors, "Expected at least one error on failure"
+ err = result.errors[0]
+ assert err.source == "gui_2._render_operations_hub_external_editor_panel_result"
+ assert "ext editor render blew up" in err.message