Define Noema's consumer-neutral event boundary

[ferueda]

Summary

• redefine Noema as a local-first derived-knowledge and event system, not an agent runtime
• end Noema core at an atomic domain-event and transactional-outbox boundary
• keep subscriptions, queues, dispatch, Eve, model execution, runs, receipts, and consumer artifacts in independent downstream systems
• replace the Content Scout runtime plan with a focused V1 event-boundary cutover plan
• add contributor guardrails and update the queued windowing plan so the rejected architecture cannot return indirectly

Review path

1. Read docs/project-intent.md, especially Event boundary.
2. Read docs/architecture.md, especially System context, The boundary test, and Rejected alternatives.
3. Read docs/roadmap.md for the new Milestone 3 and external Content Scout follow-up.
4. Read dev/plans/260728-event-boundary.md for the implementation cutover.
5. Read AGENTS.md for the enforcement rules future coding agents must follow.

Boundaries

Documentation and planning only. Runtime behavior is unchanged in this PR. The pre-V1 job/worker scaffold still exists in code and is explicitly scheduled for removal by the replacement plan.

PRs #21-#25 implement parts of the superseded Noema-owned agent runtime and should not be reviewed or merged in their current form. They need to be closed or rebuilt after this boundary lands.

Verification

• make check
• documentation terminology and stale-boundary search

Stack

This is the first PR and targets main.