Propose a rest_records config from an OpenAPI document or sample answers

The mapping assistant for a backend with no connector of its own: from an OpenAPI 3.x document (fetched through the egress guard, or pasted as JSON / YAML) and / or sample list answers, propose the rest_records endpoints — the entity types, where the rows sit, the paging style, the updated-since parameter, the id / name / updated-at fields, the relation fields — and the field → predicate mapping over the pack vocabulary, each entity with a reason and a confidence. Deterministic heuristics always; under SOURCE_MAPPING_ASSISTANT one bounded model call refines them (validated, never trusted). Nothing is written; the preview verifies the proposal by execution. Records (docs/roadmap/crm-sources-2026-09.md): a CRM row enters as FACTS — its mapped attributes become deterministic candidates under the record’s own id, never prose a model re-extracts. Source plane operator surface (docs/roadmap/raw-evidence-sources-2026-09.md) — answers a bare 404 until SOURCE_PLANE_ENABLED=1.

Required scope: brain:admin.