Should zero-width Sequences Be Counted as Zero Width in `substr_ctl`?

[brodieG]

The tension is that ANSI CSI SGR sequences are treated as zero width. Maybe the answer here is to have a substr_sgr that only treats the ANSI CSI SGR sequences as zero width.

Will have to look into how type='chars' trickles into the rest of the code, and potentially adding a conditional into how C0 sequences are counted. The dangerous part here is that will affect everything and we have to make sure we don't accidentally introduce undesired behavior elsewhere.