refactor(installer): use new async runner

lua/gopher/_utils/init.lua

@@ -3,8 +3,9 @@ local log = require "gopher._utils.log"
 local utils = {}
 
 ---@param msg string
----@param lvl number
+---@param lvl? number
 function utils.deferred_notify(msg, lvl)
+  lvl = lvl or vim.log.levels.INFO
   vim.defer_fn(function()
     vim.notify(msg, lvl, {
       title = c.___plugin_name,

lua/gopher/_utils/runner/init.lua

@@ -23,9 +23,10 @@ end
 
 ---@param cmd (string|number)[]
 ---@param on_exit fun(out:vim.SystemCompleted)
----@param opts gopher.RunnerOpts
+---@param opts? gopher.RunnerOpts
 ---@return vim.SystemObj
 function runner.async(cmd, on_exit, opts)
+  opts = opts or {}
   return vim.system(cmd, {
     cwd = opts.cwd or nil,
     timeout = opts.timeout or 2000,