Receive a tracker webhook, verify, dedupe, and enqueue.

Path parameter: adapter: Short adapter name registered via :func:bernstein.core.trackers.webhook_receiver.register_handler.

The endpoint accepts any JSON object. All verification and replay decisions are made before the body is enqueued. When verification succeeds and the delivery is fresh the parsed :class:~bernstein.core.trackers.webhook_receiver.TrackerEvent is stashed on app.state.tracker_event_queue if present so the orchestrator's normal task ingestion can drain it; if no queue is wired we simply log the event. Either way the tracker receives a 200 so it does not retry.