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>

lua/nuwiki/commands.lua

@@ -790,7 +790,15 @@ function M.smart_return()
       -- "break out of the list" behaviour on an empty bullet).
       return esc .. '0DA' .. cr
     end
-    return cr .. indent .. marker .. ' ' .. (cb and '[ ] ' or '')
+    -- nvim defaults `autoindent=on`, which inserts the previous line's
+    -- indent right after the `<CR>` we return. If we then add our own
+    -- `indent`, the new bullet is pushed one level deeper than the one
+    -- the user is continuing. Skip our copy whenever any auto-indent
+    -- mechanism is active and let Vim/Nvim insert the indent for us.
+    local auto = vim.bo.autoindent or vim.bo.smartindent or vim.bo.cindent
+        or (vim.bo.indentexpr ~= nil and vim.bo.indentexpr ~= '')
+    local effective_indent = auto and '' or indent
+    return cr .. effective_indent .. marker .. ' ' .. (cb and '[ ] ' or '')
   end
   return cr
 end