OPTIMADE trajectory JSON Lines

httk-trajectory-jsonl is a streaming holding format. The public filename convention is .traj.jsonl; the loader registers .jsonl because core strips one compression suffix and dispatches on the remaining final suffix. Thus .traj.jsonl.gz works through the normal text datastream/compression path.

The first line is an OPTIMADE 1.2.0 dense partial-data header with an x-httk-trajectory description. Subsequent lines are frame objects containing index, fractional_site_positions, and observables; variable-cell files also contain lattice_vectors. See the httk.io.optimade_jsonl module docstring for the normative schema. Values are float64 presentation values; there is no exact-token channel.

Binary framing is intentionally not included. Its framing and random-access trade-offs remain a separate design decision.

TrajectoryJsonlFile.path returns the source filename string used to construct the lazy reader.