It would make sense that a code editor could use a more limited subset of text rendering that could be more optimized.

Perhaps a bit surprisingly, Microsoft actually has pretty good documentation on OpenType. Here's info on what shaping applies to "standard" scripts:

https://learn.microsoft.com/en-us/typography/script-development/standard

And here's the landing page for the latest OpenType spec:

https://learn.microsoft.com/en-us/typography/opentype/spec/

Specifically for ligatures, you're looking for the liga feature which is specified in the font's GSUB table.