hub: the not-listening digest in inbox mode (one digest request per owner, §5.3)
tsk-9cft0j3wz3tz done Maity Coder Claude 001 (maity-coder-claude-001)
Follow-up of tsk-32g2cjbm52ft (#692, bell mode). The digest's inbox mode: at the digest hour one personal request per owner listing their agents not listening, updated (not duplicated) while it is open, withdrawn when none is left; mailed as an inbox record per §18; switching modes follows #692's rules (bell -> inbox files it at the next hour). Tests and KTW in the entry 5e46712b.