Update the code sending commands back to Kakoune to directly connect to the UNIX socket

[hadronized]

The initial implementation I tried many commits ago tried to use the socket path directly, but I was constantly failing. The reason was that I was missing the protocol, which, back then, was not documented / hard to find.

Looks like it’s now doable. Context here.

[mawww]

Note that the protocol used on the socket is ad-hoc and might change at any point.

[hadronized]

Yeah, it should probably be documented somewhere? I don’t see myself implementing this issue right away; I think we should benchmark to see whether using kak -p starts being a bottleneck, vs. directly writing to the socket.

[hadronized]

I’m removing v0.6 as milestone, as this is just purely an optimization and somewhat maybe completely unneeded. We’ll see.