New core features: Field API, Revisions, Workflow, Moderation, CMI, Auto-Admin

Six pieces went into core this sprint. Each one passed the "does every app need this" test; nothing here breaks the CRM/ERP scenario.

• Field API — 14 field types, cp_field_definitions, /aacp/fields. Mass-assignment and XSS protection now live in core, not per module.
• Node revision engine — a snapshot on every save, restore creates a new revision, a prune cron enforces the limit.
• Workflow engine — no symfony/workflow; YAML places/transitions, a capability per transition.
• Content moderation — nodes.moderation_state, opt-in per type, separate from publication state.
• Config Management (CMI) — cp:config export | status | import, deterministic YAML.
• #[CpResource] auto-admin — automatic list/form/workflow buttons from an entity.

Full write-ups are on the blog. Feedback and questions in this thread.