Verifies that run_agentic_loop pushes the correct sequence of events
(plan_ready, step_complete, step_adapted, task_complete) through the
real ws_manager, validates payloads, multi-client delivery, event
history persistence, and graceful degradation when WS is unavailable.
Fixes#445
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>