test(gemini_cli_parity_regression): migrate to send_result() (Phase 2.4)

The test_send_invokes_adapter_send test calls ai_client.send() and
asserts the return value. Migrating to send_result() with
assert res.ok and res.data == "Hello from mock adapter".

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

1 test passes.

tests/test_gemini_cli_parity_regression.py

@@ -1,4 +1,5 @@
 from unittest.mock import patch, MagicMock
+from src.result_types import Result
 
 def test_send_invokes_adapter_send() -> None:
  import src.ai_client as ai_client
@@ -9,5 +10,6 @@ def test_send_invokes_adapter_send() -> None:
   mock_process.returncode = 0
   mock_popen.return_value = mock_process
   ai_client.set_provider("gemini_cli", "gemini-2.0-flash")
-  res = ai_client.send("context", "msg")
-  assert res == "Hello from mock adapter"
+  res = ai_client.send_result("context", "msg")
+  assert res.ok
+  assert res.data == "Hello from mock adapter"