TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 5: refactor(gui_2): migrate L3163 render_tool_preset_manager_content bias_save to Result[T] (Phase 5)

Extract _render_tool_preset_bias_save_result helper from the BiasProfile
save try/except in render_tool_preset_manager_content. The imgui.button
callback drains errors to app._last_request_errors per FR-BC-4
event-handler pattern.

[pre-audit] L3163 INTERNAL_BROAD_CATCH
[post-audit] V count: 9 -> 8 (L3163 removed)

tests/test_gui_2_result.py

@@ -1018,3 +1018,53 @@ def test_phase_5_l1428_request_patch_from_tier4_result_failure():
  err = result.errors[0]
  assert err.source == "gui_2.request_patch_from_tier4_result"
  assert "tier4 backend down" in err.message
+
+
+def test_phase_5_l3163_render_tool_preset_bias_save_result_success():
+ """
+ L3163 _render_tool_preset_bias_save_result returns Result.ok=True on success.
+
+ The helper wraps the BiasProfile save try/except in
+ render_tool_preset_manager_content. On success (BiasProfile construction +
+ _cb_save_bias_profile), sets app.ai_status to "Saved: <name>" and returns
+ Result(data=True).
+ """
+ from src import gui_2
+ from unittest.mock import MagicMock, patch
+ app = MagicMock()
+ app._editing_bias_profile_name                      = "test_bias"
+ app._editing_bias_profile_tool_weights              = {"foo": 2}
+ app._editing_bias_profile_category_multipliers       = {"bar": 1.5}
+ app._editing_tool_preset_scope                      = "project"
+ mock_profile = MagicMock()
+ mock_profile.name = "test_bias"
+ with patch.object(gui_2.models, "BiasProfile", return_value=mock_profile):
+  result = gui_2._render_tool_preset_bias_save_result(app)
+ assert result.ok, f"Expected ok=True on success, got errors: {result.errors}"
+ assert result.data is True
+ assert "Saved: test_bias" in app.ai_status
+
+
+def test_phase_5_l3163_render_tool_preset_bias_save_result_failure():
+ """
+ L3163 _render_tool_preset_bias_save_result returns Result.ok=False on failure.
+
+ When BiasProfile construction or _cb_save_bias_profile raises, the helper
+ sets app.ai_status to an error message and returns
+ Result(data=False, errors=[ErrorInfo]).
+ """
+ from src import gui_2
+ from unittest.mock import MagicMock, patch
+ app = MagicMock()
+ app._editing_bias_profile_name                      = "test_bias"
+ app._editing_bias_profile_tool_weights              = {"foo": 2}
+ app._editing_bias_profile_category_multipliers       = {"bar": 1.5}
+ app._editing_tool_preset_scope                      = "project"
+ with patch.object(gui_2.models, "BiasProfile", side_effect=RuntimeError("bias validation failed")):
+  result = gui_2._render_tool_preset_bias_save_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_tool_preset_bias_save_result"
+ assert "bias validation failed" in err.message
+ assert "Error:" in app.ai_status