fix(lists): skip own indent in smart_return when auto-indent is active

nvim defaults autoindent=on, so the indent inserted by Vim/Nvim after
the <CR> we return was being doubled by our own indent prefix —
pressing Enter on a sub-item produced a deeper-nested item instead of
a same-level one. Detect any auto-indent mechanism (autoindent,
smartindent, cindent, indentexpr) and let it own the indentation;
otherwise add it ourselves so vim's noautoindent default still works.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

autoload/nuwiki/commands.vim

@@ -881,7 +881,12 @@ function! nuwiki#commands#smart_return() abort
       " newline. Indent gets dropped (matches vimwiki's break-out).
       return "\<Esc>0DA\<CR>"
     endif
-    let l:cont = l:indent . l:marker . ' '
+    " If any auto-indent mechanism is active (autoindent, smartindent,
+    " cindent, or indentexpr), Vim already inserts the previous line's
+    " indent after `<CR>`. Skipping our own indent in that case avoids
+    " doubling it and pushing the new bullet one level deeper.
+    let l:auto = &autoindent || &smartindent || &cindent || !empty(&indentexpr)
+    let l:cont = (l:auto ? '' : l:indent) . l:marker . ' '
     if l:has_cb
       let l:cont .= '[ ] '
     endif