I wrote an FAQ article for this, Castellated edge; plated half holes in board edge, but it’s not up to date for v6. I was hoping the new custom drc rule system would help, but I didn’t find a way to do it so that it would simply work, and I gave up.
IMO a castellated pad should allow normal routing and zone filling when working, and suppress DRC errors. But this may not be as easy as it seems. For example a track or a zone should connect to a pad normally and the edge should not prevent it even near the pad, but yet the same zone/track/edge combination should throw an error farther away from the pad.