The vendor API name passed to the provider as the model id.
The vendor's DriverClass — the ClassFactory key AND the per-provider voice-settings match key.
The chosen MJ: AI Model Vendors ROW id — NOT the vendor id. This is the most-specific layer of
the ModelConfiguration catalog cascade (AIModelType < AIModel < AIModelVendor), so it must
ride along with the driver identifiers: a caller that resolves a vendor in order to mint a session
also needs it to read that session's catalog defaults.
The chosen MJ: AI Vendors row id (empty string when the vendor row carries none).
The vendor identifiers a resolved realtime model runs under.