M2: Notify / update plane stub (long-poll) #31

Context

PRD: docs/PRD.md §7 (update plane), §10 (CF Queues v1 / NATS self-host). Milestone M2.

Goal

Let workers learn that “work is available” without busy-spinning the object store. Ship a portable stub: long-poll (or equivalent) over HTTPS first; document how CF Queues can replace it later without API breakage.

Out of scope

• Implementing Cloudflare Queues binding in production
• NATS JetStream (self-host later)
• Guaranteed exactly-once delivery

Suggested approach

• Interface for “notify / wait for change” under internal/ (name flexible)
• HTTP long-poll endpoint scoped to org/project (and optionally session/job queue)
• In-memory wake for tests; Store-backed dirty flag or generation counter OK for M2

Acceptance criteria

• Client can long-poll and return when a session message or job is created (same process)
• Timeout returns empty/204 with documented semantics
• README notes: CF Queues / NATS as future drivers behind the same interface
• make check green offline

Dependencies

Sessions/messages/jobs on serve path; pairs with attach.

How to hand to Aixgo Code

Apply ax:go after or with attach.