Initial 100, capacity 300, world tree +20 per 10 game minutes. Each boundary
pays registered upkeep demand before storing surplus; overflow is discarded
and recorded, 0 stops the whole tower. Furnace offers are judged after
generation and demand payment. New saves carry mana_reserve and Operations
rollback includes it; legacy saves keep a 0..300 amount and reject others.
Outage tests that relied on Mana 0 persisting now hold the outage with a
disabled demand sink, since the world tree recovers at the next boundary.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
