Add notification digest preferences to contract

[haasonsaas]

Summary

• add digest preferences to NotificationPreferences
• add queued delivery status for batched notifications
• regenerate Go, Python, and TypeScript notifications bindings

Testing

• buf lint
• go test ./... -count=1
• npm ci
• npm run check:package

[cursor]

PR Summary

Medium Risk
Updates the notifications protobuf contract by adding a new preferences message/field and a new delivery status enum value, which can break or require updates in downstream clients/servers that switch on enums or expect stable message shapes.

Overview
Expands the notifications API contract to support digest/batching configuration and a new delivery lifecycle state.

NotificationPreferences now includes repeated digest_preferences entries (new DigestPreference message with category/channel, window, and enabled flag), and DeliveryStatus adds DELIVERY_STATUS_QUEUED for batched notifications. Regenerates the Go, Python, and TypeScript generated bindings to reflect these schema changes.

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