* fix: show float title when border is nil
Problem: the float title was only shown via the native `nvim_win_set_config`
path, which requires a border to render. The guard `config.float.border ~=
'none'` did not account for `nil`, which is the default — so users with no
explicit `border` config never saw the path title in the floating window.
Solution: require both `~= nil` and `~= 'none'` before using the native
title. In all other cases (border nil, 'none', or nvim < 0.9), fall back to
`util.add_title_to_win`, which renders a child floating window for the title.
Based on: stevearc/oil.nvim#683
* refactor: drop nvim-0.9 version checks in float title logic
0f386bb69c