Register a webhook

HTTPS only, on the standard port (443), with no credentials in the URL; the host must be public, and the URL is checked before it is stored and again at every delivery. Redirects from the endpoint are not followed. Deliveries carry X-ZenMode-Signature (hex HMAC-SHA256 of the exact raw request body, keyed with the webhook's secret) and X-ZenMode-Event. A task.completed or task.failed body is { event, data, timestamp }, where data.result is the task's result. On a free or unconfirmed LinkedIn plan the connection request is sent without a note, and the task result carries note_dropped: true with note_dropped_reason: "free_or_unconfirmed_plan". The webhook body carries the same two fields in data.result.