During the signaling period, BIP-110 nodes reject blocks that do not signal support. What, then, is the purpose of the 55% activation threshold?From the perspective of a BIP-110 node, would the threshold not always appear to be met, since every block it accepts during that period must already be signaling? Or is the 55% calculated using blocks from the full proof-of-work chain, including blocks that BIP-110 nodes consider invalid?