"""SITL replay fixture builder (AZ-598).

Vertical-slice tooling that produces the `outbound_messages_<fc_kind>_<host>.json`
+ `observer_<fc_kind>_<host>.json` fixtures consumed by the b75 sitl_observer
in offline FDR-replay mode.

Strategy: reuse the production `gps-denied-replay` CLI + `ReplayInputAdapter`
to drive the SUT pipeline against a 1 fps MP4 encoded from the FT-P-01 still
image set and a synthetic stationary tlog. Read the resulting FDR JSONL and
project each per-frame outbound estimate into the fixture schema. This avoids
building new SUT-side frame ingestion infrastructure.

Only the FT-P-01 still-image variant is supported in this batch; FT-P-02 etc.
will land as follow-up tickets.

Public symbols live on the submodule `build_p01_fixtures`; we deliberately
do NOT re-export them on the package namespace because the function and
the submodule share the name `build_p01_fixtures` and the function would
shadow the submodule for `import …build_p01_fixtures as bp` callers.
"""