In a state where the governor has power (Do (any) US State Governors have legal authority to preemptively pardon persons of a state crime?) to pardon a capital crime before prosecution, does a prosecutor who learns of the governor's intent to pardon have any way to force prosecution?
There is no recourse
The Pardon results in the pardoned person having no liability for the act, no matter if it was a crime or not, and no matter whether the pardon pre-dates a prosecution. There is no legal or political way to appeal a pardon. There isn't even a way to take back a pardon! As a result, the prosecutor or the next governor can do nothing.