Cron was the only execution path that never called end_session(),
leaving ended_at = NULL permanently. This made cron sessions invisible
to hermes prune --older-than and indistinguishable from active sessions.
Captures session_id in a local variable before agent construction so
it's available in the finally block even if AIAgent() fails, then calls
end_session(session_id, 'cron_complete') before close().
Cherry-picked from PR #2979 by ygd58. Fixed bug: original PR called
end_session() with zero arguments (TypeError — method requires
session_id and end_reason).
Fixes#2972.
Co-authored-by: ygd58 <ygd58@users.noreply.github.com>
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