Import the org playbooks as agents

Creates one agent per stored playbook definition (agent-refactor-spec §13): the handle comes from the playbook name, and the published version mirrors the playbook. Idempotent and additive — a playbook that already has an agent comes back in skipped, and the source playbook documents are never modified. Every playbook has its own error boundary: a legacy document the current schema refuses lands in failed instead of failing the whole import. Authorization: organization administrators only. Response: { data: { created: [{ playbookId, agentId, handle }], skipped: string[], failed: [{ playbookId, error }] } }.