Update API specifications with fern api update

[github-actions]

Update API specifications by running fern api update.

---

Note

Medium Risk
Webhook event type string changes are a breaking contract for subscribers; diagram-content socket and broadcast schemas expand the public API surface clients must implement against.

Overview
Regenerates openapi.json from fern api update, aligning published API types with the current Fern spec.

Webhooks: WebhookEventType values change from model-connection.create style to model-connection:created (colon + past tense). New WebhookEvent, WebhookEventCollection, and WebhookEventOperation schemas describe webhook payloads structurally.

Realtime / sockets: Documents diagram content collaboration: client diagram-content-subscribe / diagram-content-unsubscribe, server diagram-content-broadcast, plus SocketMessages, SocketMessageType, and related subscription/broadcast schemas. Adds DocumentBroadcastType and QueryBroadcastType enums (added, initial, modified, removed).

Other: DiagramContentNullable (DiagramContent | null); aiFeaturesEnabled and oauthLandscapeWriteEnabled no longer declare OpenAPI default: true on organization schemas.

^{Reviewed by Cursor Bugbot for commit d3b20c1. Bugbot is set up for automated code reviews on this repo. Configure here.}