Parse agent traces

[lhoestq]

Supports claude_code, codex and pi

JSON Lines files are parsed so one file = one row

The resulting row has three fields: harness, session_id, traces, and file_name with features:

AGENT_TRACES_FEATURES = datasets.Features(
    {
        "harness": datasets.Value("string"),
        "session_id": datasets.Value("string"),
        "traces": datasets.List(datasets.Json()),
        "file_name": datasets.Value("string"),
    }
)

cc @cfahlgren1

[HuggingFaceDocBuilderDev]

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[cfahlgren1]

parsing seems to match