feat(agents): run Playbooks inside a Crew #170

Problem

Crews (the crews/* stack, #145 through #152) and Playbooks (the codex/playbooks-* stack, #156 through #164) are landing as two separate systems. A Crew is a roster of Peer Agents a Captain proposes and I approve; a Playbook is a deterministic multi-step run with pinned persona snapshots and gated publication. Today neither knows about the other, so a Captain cannot hand a Crew a playbook to execute, and a playbook run cannot draw its step workers from an approved roster.

Goal

Once both stacks are merged into j5/main, incorporate Playbooks into Crews so a Crew can run a playbook as a unit.

Things I want settled in the design before any code:

• How a Captain starts a playbook run from a Crew, and whether that run's steps fill seats on the existing roster or spawn seats of their own that go through the normal roster gate.
• Which Crew lifecycle verbs apply to a run in flight. A Crew stops and archives as a unit (feat(agents): a Crew stops and archives as a unit #151), so a running playbook has to settle with it.
• Where the run shows up. Playbook runs already surface in boards, timelines, and inboxes (feat(playbooks): review runs from boards timelines and inboxes #162); Crews show up on the Fleet page. I want one place to see both without duplicating either.
• Whether run outputs are delivered as versioned artifacts the way Crew deliveries are, so the Artifacts page stays the single place for agent-produced documents.

Constraints

• Blocked until both stacks are merged. Do not start on this while either is still in review.
• Follow FORK.md: keep the integration under apps/*/src/j5/ and record any upstream touch in the sanctioned-cases inventory.
• One concern per PR when this turns into implementation work.