Instead of requesting the full tree as a JSON and extracting the focused
window with `jq`, use `kitten-@-ls`'s `--match` flag. This further
improves the performance.
Also remove the commented code using recursive descent because it is not
up-to-date anymore.
kitten-@-ls(1) is unfortunately a bit slow (100ms) which is noticeable
when launching new windows using `get_cwd`. Make `get_cwd` faster (down
to 25ms) by communicating directly with the socket instead of using
`kitten`.
Since I run kitty with --single-instance, xcwd does not work for it.
Replace it with a short script that retrieves the CWD for the focused
window through the remote-control ls command.
This changes the current behaviour slightly, since now only terminals
are used and not any X window (which I rarely used or needed) and that
the working dir of the shell running in kitty will be used and not of
any deeper children. I'm still unsure if I want the latter back, but
will figure this out in the future.
This is an addendum to 0139294831 ("Use kitty instead of st as
terminal").
