The majority of Constitutional scholars would say that the Constitution does not codify one way or another the issue of state secession.
Secession is contrary to the first stated purpose of the Constitution.
Violent secession is contrary to several more of those stated purposes.
The Constitution is not a national suicide pact. That’s axiomatic. Wouldn’t be much of a national Constitution if it was.
But a majority would say Congress can make the general rules for acts of states, as Article IV says.