Problem: override.lua still has its own copies of ext_map,
filename_map, and resolve(), duplicating the newly extracted
resolve module.
Solution: replace local tables and resolve() with imports from
nonicons.resolve. Update all *_by_filetype overrides to use
resolve_filetype() instead of raw ext_map[ft], gaining ft_map
fallback and direct mapping key lookup.
Problem: the original ya2s/nvim-nonicons fork diverged enough that
maintaining it as a fork was pointless. The set_icon() approach broke
with modern nvim-web-devicons, and the extensions directory coupled
integrations that belong in user config.
Solution: from-scratch rewrite with function wrapping + table mutation
override engine, vim.g.nonicons config pattern, vendored mapping with
integer codepoints, health check, vimdoc with recipes, and no built-in
plugin integrations.
