Deregistration only removed the base group folder, leaving the tribunal
reviewer/arbiter runtime behind: DB session rows keyed as "<folder>:reviewer"
/":arbiter" and on-disk dirs data/sessions/<folder>-reviewer/-arbiter (plus
ipc/workspaces variants). Include those role-suffixed variants in both the
sessions DELETE and the disk cleanup so a deregistered room leaves nothing.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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