Retrieve the core practitioner record by ID

Returns the core practitioner record for the specified identifier from the tenant source. Use this to retrieve low-level core record data as opposed to the enriched operational view returned by GET /practitioners/{id}. {id} is a crosswalk ID, not the certifyPractitionerId; the handler looks the record up directly by tenant source and crosswalk ID, a different lookup mechanism than GET /practitioners/{id}, and applies no enrichment — no credentialingStatus or nextCredentialingDate derivation, and no operational-view overlay merge.