integrate harpoon and no neck pain

TODO

when there’s only harpoon window, we are stuck. choosing an item from harpoon window causes error
- open harpoon and delete the main editor window will lead to this bug
when the editor has two windows and harpoon is open, closing one editor window causes harpoon to span to half screen size
when use keybind like <leader>hh when cursor is in harpoon menu, it’s gonna open the file in harpoon menu and mess up everything
ctrl-o/i in harpoon menu messes things up