feat(mux): add support for wezterm

[onelesd]

Description

This adds support for wezterm to the mux implementation.

Supports only "split" mode which mimics how sidekick embeds sessions w/o mux. There is no technical limitation to adding support for other modes - I just don't need them.

This was created w/ claude code and reviewed with my own eyes.

[ljie-PI]

Can I use wezterm on Windows with this change

[onelesd]

Can I use wezterm on Windows with this change

@ljie-PI i don't see why not - i don't have a windows machine to test on but feel free to give it a try and report back.

[MaxRehnberg]

Hey man, awesome PR, I use this every day. I did however run into some issues. ´get_pid_from_tty´ does this check:

local function get_pid_from_tty(tty)
  if not tty then
    return nil
  end
  ...

However, this only catches Lua nil/false, and it seems like wezterm cli list --format json sometimes returns tty_name as null, witch parses to vim.NIL, which is truthy. I monkeypatched this as such in my local config:

-- Line 193
local ok, panes = pcall(vim.json.decode, table.concat(output, '\n'), { luanil = { object = true } })

To parse null-values as lua nils. It works for me, but it would be nice to get this into the official version as well.