Add cost-safe webhook automation support - #264

Summary

• add opt-in, Cloudflare Queue-backed webhook delivery with an atomic D1 outbox, bounded retries, daily and endpoint limits, Standard Webhooks signing, secret rotation, reconciliation, retention, and automatic endpoint pausing
• define exact, stable snapshots and canonical examples for all 22 webhook events in the generated OpenAPI contract, including signed test markers and correlation/causation metadata
• add Webhooks administration with Overview, Endpoints, Event explorer, and Deliveries views; Event explorer can preview generated or current content, inspect payload/schema/headers, print locally without side effects, or send a signed test through the normal delivery path
• keep the first endpoint form visible as an empty-state setup step, then move Add endpoint and Edit into a shared modal once endpoints are configured
• add Queue usage accounting, explicit deployment opt-in, a Stripe-like local listener, and microfeed webhook sample discovery from each instance's OpenAPI document
• add a standalone Content automation documentation section, runnable agent-oriented recipes, and a persistent automation skill with signature verification, test-event gating, durable acknowledgement, deduplication, and loop prevention

This gives people and deployed agents a cost-bounded way to discover exact payloads and react to content changes without polling, while keeping webhook infrastructure optional for ordinary microfeed deployments.

Related issue

N/A

Testing

• yarn check
• git diff --check
• yarn lint:openapi
• focused Admin, CLI, OpenAPI, webhook, and Worker tests
• CLI packaged smoke tests
• documentation generation and validation
• automation skill validation

The complete check passes all unit and Worker tests and verifies the production Worker, CLI package, generated API contract, and documentation builds.

Screenshots

N/A — no screenshots were requested. The Admin routes and components are covered by component and Worker tests.

Risks

• Deployments must explicitly opt in with yarn manage deploy --enable-webhooks; ordinary deployments do not create or bind a Queue.
• Event explorer previews and local terminal prints are free and side-effect-free, while endpoint sends use the normal Queue, retry, budget, delivery-history, and failure-streak behavior.
• The D1 migrations add webhook storage and named API-key scopes. Existing credentials retain read/write compatibility.
• Snapshot restores intentionally omit deployment-encrypted webhook endpoints and delivery history; administrators recreate endpoints after restoration.
• Delivery is at-least-once, so receivers must deduplicate delivery IDs and durably acknowledge work before long-running processing.

Checklist

• This pull request contains one focused change.
• Tests were added or updated when behavior changed.
• Documentation was updated when commands or public behavior changed.
• No secrets, private configuration, production data, or generated files are included.