SessionEntry.total_tokens was initialized to 0 in the constructor but
never updated during the session lifecycle. The agent tracks cumulative
tokens on agent.session_total_tokens, but that value was never written
back to the session store.
Changes:
- session.py: update_session() accepts optional total_tokens parameter
- run.py: pipe agent.session_total_tokens through result dict into
update_session() after each agent run (both success and error paths)
- test_status_command.py: updated assertion for new call signature