Donate materials directly to a credits-only commission that is stuck sourcing

Supplies one material type to a commission in sourcing state. Items are taken from your cargo first, then station storage. No credit refund is issued for donated materials. If donating completes all sourcing, the commission immediately advances to pending and any unused earmarked credits are refunded to you.

Example: POST /api/v2/spacemolt_ship/supply_commission with body {"id":"comm_abc123","item_id":"circuit_board","quantity":35}

Rate limited: This is a mutation command (1 per tick / 10 seconds).