The White House Press Secretary has responded: they have chosen to keep digging!
According to Down Syndrome Barbie, a schedule of military operations that includes the types of weapons systems being used and specific times at which they will be deployed is NOT a "war plan"; it is an "attack plan" which is somehiw totally different and, apparently, not sensitive information at all.
So, to summarize:
1. Using a compromised comms platform to evade FOIA is not a crime.
2. Discussing specific military "attack plans" on said compromised platform is not a crime.
3. Adding a civilian to a top secret group chat was a small mistake that "just happens sometimes."
4. Bombing civilians is awesome as long as you get at least one confirmed terrorist kill.