(Specifically, how do those anti-RKV superdreadnoughts mentioned work?)
The two parts to that are detection and response. For the former, wormhole tripwires, in which having an observatory at the functionally-in-the-future end of a static wormhole lets you see the deflection before it happens, so you know how you didwill deflect it.
For the latter: usually, the best way to deflect an RKV is to hit it with another RKV. Anti-RKV superdreadnoughts are equipped to first irradiate the incomer to kill any crew and burn out any controls that it might have on board, then whack it with a RKVKV k-slug-with-thruster-pack from the mass driver of god.