Poll an async query job.

Returns the current status of a query submitted asynchronously via POST /v1/data/query (DVT-708, ADR-0050). While running, polls the engine's stateless /internal/query/poll endpoint (re-sending the resolved connection bundle so the engine carries no per-job state). When the job has already reached a terminal state, serves the result from the in-memory cache (when still warm) or returns the terminal status without rows (cache expired).

AUTHZ: the calling actor must be in the same org as the job AND their warehouse identity (the role dimension, computed the same way as the submit path) must equal the job's frozen role_dim — so an oauth_passthrough user cannot poll another user's job, and a differently-role-mapped service caller cannot poll a job keyed for a different role. Mismatch → 404 (indistinguishable from not-found).