Read a transparent seat-split maintenance price

No authentication required when enabled. Founding royalties require a completed founding-cycle payment; a paid founder keeps that right after leaving. A seat shortfall leaves the next billing attempt scheduled. An underfunded cycle does not post work or charge other seats more. Returns maintenance/N + fee, current and next subscriber shares, the share if one seat leaves, a 10-seat comparison, the founding-funder royalty dial, and the sunset signal (at_risk with reason: no_subscribers, last_cycle_shortfall, subscriber_balance, paused) so subscribers see a dying feed before it pauses.