Add, debug, and manage webhook providers in the joelclaw webhook gateway. Use when: adding a new webhook integration (GitHub, Stripe, Vercel, etc.), debugging webhook signature failures, checking webhook delivery, testing webhook endpoints, registering webhooks with external services, or reviewing webhook provider implementations. Triggers on: 'add a webhook', 'new webhook provider', 'webhook not working', 'webhook signature failed', 'register webhook', 'webhook debug', 'verify webhook', 'add Vercel/GitHub/Stripe webhook', 'webhook 401', 'test webhook endpoint', or any external service webhook integration task.