Expose webhook and Slack/email delivery endpoints for agent events

[awyoo]

Context

While documenting the Spectre + Stellar agent cookbook for wraith-protocol/docs#8, the docs source-of-truth exposed REST endpoints for agent create/chat/status/conversations/invoices/notifications and chat tools for scheduled payments, name registration, payment scanning, funding, and privacy checks.

The cookbook recipes also need external delivery hooks for inbound payment alerts, scheduled payroll failures, and privacy-check reports. Today those events are available through in-app notifications/pending actions, but there is no public REST surface to configure webhook, Slack, or email destinations.

Requested follow-up

• Add an API to register per-agent notification sinks, such as webhook URL, Slack webhook URL, and email recipient.
• Deliver signed event payloads for payment_received, scheduled_payment, schedule_error, and privacy_alert.
• Include retry/backoff and delivery status in agent notifications or a delivery log endpoint.
• Document request/response DTOs so the docs cookbook can replace polling fallbacks with first-class webhook examples.

Source files checked

• src/agent/agent.controller.ts
• src/notifications/notification.controller.ts
• src/agent/tools/agent-tools.service.ts
• src/scheduler/scheduler.service.ts