Implement negative momentum cancellation rule in action rolls

[cwegrzyn]

See Starforged rulebook p38 and Ironsworn p13

[cwegrzyn]

This has two parts:

• [ ] A way in a move node to indicate that the action die is canceled because of negative momentum
• [ ] An update to the action roll logic to add the above modifier when appropriate

@zkat what do you think about the mechanics piece? One idea: we add a "cancel" node analogous to the reroll node: you say which die should be cancelled and a reason why (e.g., "matched negative momentum (-4)"). I think other mechanics can cancel dice, so this would be generally useful. In that case, we'd also want:

• [ ] A command to add a cancel node to an existing move

[zkat]

@cwegrzyn What do you think of just having a bool flag action-canceled=true and then I can render it crossed out and adjust the roll total?

[cwegrzyn]

I looked through the Ironsworn, Delve, Starforged, and Sundered Isles and I couldn't find anything else that cancels the action die, so I think it's fine to have an action-canceled on the initial roll. Maybe we can make it so that it can be boolean or a string-- if it's a string that can give a cancellation reason (maybe shown in a tooltip?), which should always be "matched momentum -X"... but you never know what crazy stuff people might do in homebrew?