b7d2a6c61a
<sfile> inside a command! body is evaluated at execution time, not at
definition time. When :NuwikiInstall is run interactively there is no
sourcing context, so <sfile> expands to nothing and the path collapses
to ./scripts/download_bin.vim — producing E484.
Fix: capture the path in s:plugin_root immediately while the script is
being sourced, then reference that variable from the command body.
Also hoist :NuwikiInstall above the early `finish` for Neovim so the
command is available in both editors (Neovim routes to
require('nuwiki.install').install(), Vim sources the download script).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>