Neovim: completion menu auto-inserts first match

Symptom

Typing vim. in a Lua buffer opens the completion menu but immediately inserts
the first match (“F” from vim.fn). Deleting it closes the menu with no way to
reopen it mid-insertion.

Cause

Default completeopt is menu,preview, which pre-selects the first item.

Fix

Add to init.lua:

o.completeopt = "menu,menuone,noselect"

• menuone opens the menu even with a single match
• noselect prevents auto-selection, so nothing is inserted until confirmed
  with <C-n> or <C-y>