test(api_events): migrate 2 sites to send_result() (Phase 2.8)

The test_send_emits_events_proper and test_send_emits_tool_events tests
both call ai_client.send(). Migrating to send_result() + assert result.ok.

Changes:
- Rename ai_client.send(...) to ai_client.send_result(...) (2 sites)
- Add assert result.ok (2 sites)
- Add "from src.result_types import Result" import

4 tests pass.

tests/test_api_events.py

@@ -1,6 +1,7 @@
 from typing import Any
 from unittest.mock import MagicMock, patch
 from src import ai_client
+from src.result_types import Result
 
 
 class MockUsage:
@@ -60,7 +61,8 @@ def test_send_emits_events_proper() -> None:
         ai_client.events.on("request_start", start_callback)
         ai_client.events.on("response_received", response_callback)
         ai_client.set_provider("gemini", "gemini-2.5-flash-lite")
-        ai_client.send("context", "message", )
+        result = ai_client.send_result("context", "message", )
+        assert result.ok
         assert start_callback.called
         assert response_callback.called
         args, kwargs = start_callback.call_args
@@ -103,5 +105,6 @@ def test_send_emits_tool_events() -> None:
             tool_callback(*args, **kwargs)
 
         ai_client.events.on("tool_execution", debug_tool)
-        result = ai_client.send("context", "message", enable_tools=True)
+        result = ai_client.send_result("context", "message", enable_tools=True)
+        assert result.ok
         assert tool_callback.call_count >= 1