“Biden’s senility is irrelevant. He isn’t in charge.”
For the most critical aspects of national security he absolutely is in charge and he alone has to call the shots. The military is not going to do nor not do something major on the authority of Valerie Jarrett, Jill Biden, or anyone else.
Biden has the authority. But if he's senile, the real person in charge is whoever is pulling his strings.
Besides which, today's military ignores Constitutional authority when it wishes. Trump wanted to use the military to quell the D.C. rioters, but the generals effectively vetoed Trump.