Export session trajectory

Export the session trajectory in the Agent Trajectory Interchange Format (ATIF v1.7, RFC 0001): steps, user messages, agent reasoning, tool calls and their results, and token and cost metrics. Reason tool calls made inside codemode appear as tool calls linked to their parent call by extra.parent_tool_call_id. A standard session masks the run's secret values, known credential shapes and any unbroken run of 40 or more letters, digits, - or _, which includes hashes. An ephemeral session masks only the run's secret values, as [redacted-secret], and credentials Reason issues. A tool call's arguments and output are exported whole; extra.fidelity counts the redaction markers and the tool events exported from a 4,000-character preview. agent.version is the Reason release that ran the latest turn. Each subagent Session the session started is embedded in subagent_trajectories, and final_metrics totals include them; final_metrics.extra.session_totals holds the session's own.

_{Scope: sessions:read}