Add Push API Core (PushManager and Subscriptions)

Proposal

Provide Push API primitives for subscription lifecycle and payload delivery wiring.

Scope:

• Expose PushManager on service worker registration.
• Implement subscribe, getSubscription, and unsubscribe.
• Model PushSubscription shape and endpoint/keys data.
  Technical Notes:
• Use injected push transport backend.
• Integrate with Notifications and Permissions constraints.
  Acceptance Criteria:
• Subscriptions are origin-scoped and retrievable.
• Unsubscribe removes active subscription state.
• Tests cover permission-denied and backend failure paths.
  Out of Scope:
• Real vendor push service integration by default.
• Full encrypted payload stack in first pass.

Description

Add Push API core primitives: PushManager access on service worker registration, subscribe/getSubscription/unsubscribe, and subscription object modeling.

Background

Push is central to modern engagement workflows and service-worker-driven messaging. A minimal subscription lifecycle is sufficient for many test and integration scenarios.

Specification

• Push API specification: https://w3c.github.io/push-api/
• Integration expectations with Notifications and permissions

Start by locating the service worker registration, Notifications, and Permissions integration points, then review the linked Push API specification. Define how the injected push transport supports subscribe, getSubscription, and unsubscribe, including origin scoping and subscription endpoint/keys data. Done means the acceptance criteria and permission-denied and backend-failure tests are covered.