If I ignore a subpoena, I go to jail.

If you get a subpoena, it's probably issued by a court and judge can order you to jail if you don't comply

But if you get a subpoena from Congress, that's a different story. They need to go to court get an order from the judge to order you to appear and then if you don't appear, the judge can send you to jail. Congress can just send anyone to jail for failing to answer a subpoena.

(And, yes, I know all about Inherent Contempt. I also know why it hasn't been used to arrest anyone in nearly 100 years)

A judge?

But they've said they aren't going to waste any more time waiting to litigate because that's what Trump wants - his MO is to delay, delay, delay.

Instead, they're cutting straight to the chase and treating every instance in which a witness disobeys a subpoena as another instance of impeachable obstruction of justice. This makes sense since the point of the subpoena is to get testimony or information to determine whether and which impeachable offenses have been committed - in other words, impeachment would be the likely result of anything they get from the subpoena. So they're simply making the defiance part of the impeachment, not an impediment to it.

They will probably still go to court to fight for certain documents, but they're not going to wait for court resolution in order to proceed with impeachment.