The deadline for residency should be BEFORE the November election so people can’t plan ahead for runoffs.
The state law requires that you be a valid voter for the general election to compete in the runoff.
However, a federal law passed in 1994 requires registration to be open up until 30 days before “an election”.
And a lawsuit was “settled”, with the consent decree waiving the legal requirement, and allowing registration up until december 5th.