Implement TDD bug-capture tests for bug #570 where `agents session create`
fails because `_get_session_service()` calls `container.db()` which does
not exist on the DI Container class (AttributeError). Same root cause as
bug #554.
Behave BDD scenarios tagged @tdd_bug @tdd_bug_570 @tdd_expected_fail
exercise the real DI path (no mocks). Includes Robot Framework integration
smoke tests with self-inverting helper and ASV benchmark baseline.
ISSUES CLOSED: #631
