Artifactual BA.2 recombination node

[hyanwong]

We know that node 1030562 (classified as "BA.2"), which has 166285 descendant samples, is not robust (net_supporting_loci_rgt=3), and the breakpoint is at the far right of the genome (pos 27382). This is the copying pattern, which looks pretty iffy to me.

This discussion is just to keep track of this otherwise rather influential recombinant. E.g. it would probably be worth checking at some point whether this is still a recombinant when we try matching in allowing intermediate nodes during the matching process, and what the HMM cost etc is.

[hyanwong]

I have been chopping it out of ARG plots by the simple hack of doing arg.keep_intervals([[0, 27382]], simplify=False).trim().