Decode and validate a server-supplied checkpointTapscript against policy.
Every offchain send/claim builds its checkpoint outputs' server-claim leaf
straight from this script — undecodable, sub-floor or wrong-pubkey values
let the operator sweep an in-flight checkpoint before it settles. This is
the sole gate: callers must use the returned script rather than decoding
their own copy.
Decode and validate a server-supplied
checkpointTapscriptagainstpolicy.Every offchain send/claim builds its checkpoint outputs' server-claim leaf straight from this script — undecodable, sub-floor or wrong-pubkey values let the operator sweep an in-flight checkpoint before it settles. This is the sole gate: callers must use the returned script rather than decoding their own copy.