test(gui2_mcp): migrate to send_result() (Phase 2.5)

The test_mcp_tool_call_is_dispatched test calls ai_client.send() and
asserts the MCP dispatch function was called. Migrating to send_result()
+ assert result.ok.

Changes:
- Rename ai_client.send(...) to ai_client.send_result(...)
- Add assert result.ok
- Add "from src.result_types import Result" import

1 test passes.

tests/test_gui2_mcp.py

@@ -2,6 +2,7 @@ import unittest.mock
 from unittest.mock import patch, MagicMock
 from src.gui_2 import App
 from src import ai_client
+from src.result_types import Result
 
 def test_mcp_tool_call_is_dispatched(app_instance: App) -> None:
  """
@@ -44,12 +45,13 @@ def test_mcp_tool_call_is_dispatched(app_instance: App) -> None:
   mock_chat.send_message.side_effect = [mock_response_with_tool, mock_response_final]
   ai_client.set_provider("gemini", "mock-model")
   # 5. Call the send function
-  ai_client.send(
+  result = ai_client.send_result(
    md_content="some context",
    user_message="read the file",
    base_dir=".",
    file_items=[],
    discussion_history=""
   )
+  assert result.ok
   # 6. Assert that the MCP dispatch function was called
   mock_dispatch.assert_called_once_with("read_file", {"file_path": "test.txt"})