Buy Psbt:
0 - Taker received amount
1..n - Maker rune change
n+1 - Protocol rune fee
n+2 - Edict
n+3..m - Maker received sats amount
m+1 - Protocol sats fee
Sell Psbt:
0 - Taker rune change
1..n - Maker received rune amounts
n+1 - Edict
n+2..m - Taker received amount
m+1 - Protocol sats fee