Graftroot: Private and efficient surrogate scripts under the taproot assumption

Ryan Grant asked about unilateral key rotation in a multisig setup that wouldn't invalidate the interests of other parties without requiring any on-chain transactions. The response was that it is possible, but the word "rotation" may not be accurate because it doesn't invalidate any keys. The original setup remains able to sign, and a new key can be added to sign along with everyone else if all parties agree. However, the old key can still sign as well.