balance checking on edits (publishes+ channels)

The balancer checker doesn't take into account the existing bid on a channel/publish when editing. So you may have enough to cover it including the bid, but it won't let you submit the tx.

Start by locating the balancer checker used when editing publishes and channels, then trace how an existing bid is represented before transaction submission. Reproduce an edit where the available balance covers the bid, and confirm that the transaction can be submitted without incorrectly failing the balance check.

Written by the indexing model from the issue text.