Two corrections applied during Plan 5 execution:
- Task 2 test helper writeSession now joins a sessions/ subdir so it
matches the handler's <brainDir>/sessions/*.jsonl scan path.
(The original heredoc would have produced 0 records in tests.)
- Task 6 grew a Step 1.5 to update the session_log MCP tool's
final_status description, picking up a spec requirement that
didn't translate into a task in the original plan.