chore(pyproject): remove send_result deprecation filterwarnings (Phase 6.3)

Removes the filterwarnings entry that silenced the DeprecationWarning
emitted by the now-removed send() function. The filter was added in
data_oriented_error_handling_20260606 (commit 73cf321c) specifically
to silence the send() deprecation; no other deprecation in the
codebase was silenced by it. Now that send() is gone, the filter is
obsolete.

Verification: 'uv run rg ignore:Use ai_client.send_result pyproject.toml'
returns 0 hits.

pyproject.toml

@@ -43,9 +43,6 @@ dev = [
 ]
 
 [tool.pytest.ini_options]
-filterwarnings = [
-    "ignore:Use ai_client.send_result.*:DeprecationWarning",
-]
 markers = [
     "integration: marks tests as integration tests (requires live GUI)",
     "clean_install: clean install verification (opt-in via RUN_CLEAN_INSTALL_TEST=1)",