Public key recovery for EC leaves in P2MR (BIP-360)

The recent discussions highlight a significant issue with the script spend path in blockchain technology, particularly concerning the necessity to reveal P. This revelation becomes problematic in scenarios such as Q-day, where spends in the mempool are susceptible to attacks. During such events, the security of coins is compromised, leading to them being frozen until keypath spends are effectively disabled. This situation renders the output type unusable post Q-day, prior to the disabling of EC, due to the location of Post-Quantum Cryptography (PQC) paths within the scripts. This inherent vulnerability necessitates a reassessment of current practices and the development of more robust solutions to enhance security in post-quantum scenarios.