test(ai_client): rename send_result to send in 22 remaining test files

Batch rename of 22 test files. 62 references renamed total.

The full test suite is now GREEN again, matching the pre-rename baseline
from Task 1.1. Pure mechanical rename. No behavior change.

Files affected: test_ai_cache_tracking, test_ai_client_cli,
test_ai_client_result, test_api_events, test_context_pruner,
test_deepseek_provider, test_gemini_cli_* (3 files), test_gui2_mcp,
test_headless_* (2 files), test_live_gui_integration_v2,
test_orchestration_logic, test_phase6_engine, test_rag_integration,
test_run_worker_lifecycle_abort, test_spawn_interception_v2,
test_symbol_parsing, test_tier4_interceptor, test_tiered_aggregation,
test_token_usage.

Note: spec estimated 24 files; actual is 22 (test_deprecation_warnings
no longer exists, and 1 fewer file than spec's list).

Refs: conductor/tracks/send_result_to_send_20260616/

tests/test_token_usage.py

@@ -32,7 +32,7 @@ def test_token_usage_tracking() -> None:
   mock_response.text = "Mock Response"
   mock_chat.send_message.return_value = mock_response
   ai_client.set_provider("gemini", "gemini-2.5-flash-lite")
-  result = ai_client.send_result("Context", "Hello")
+  result = ai_client.send("Context", "Hello")
   assert result.ok
   comms = ai_client.get_comms_log()
   response_entries = [e for e in comms if e.get("direction") == "IN" and e["kind"] == "response"]