Pipeline orchestration.
Drives a request through the stages, authenticate, authorize, classify,
resolve, transform, dispatch, reverse-transform, egress (docs/04 §1),
wiring the other crates together through osproxy-core types and
osproxy-spi traits. It owns no low-level wire or parsing detail.
M1 lands the write-path core: [build_write_batch] turns a resolved routing
decision plus the request body into the epoch-stamped
WriteBatch the sink delivers. M2 adds the
get-by-id read path: the [Pipeline] maps a client's logical id to the
physical id, fetches it through the Reader seam,
and strips the injected tenancy fields so the client sees its logical
document, the write→read round-trip symmetry the model rests on.