Get Webhooks

List the account's per-agent webhook configuration(s).

Secrets are masked. Pass agent_id to inspect a single agent's webhook. The full secret is only ever shown once, by set_webhook.

Returns {"webhooks": [...], "count"}: each has agent_id, url, masked secret, signature_header, protocol, capabilities and created_at. An empty list means no webhook is set, so events wait for poll_events. HTTP 404 if agent_id is not an agent on this account.