adapter-dom.sx: if/when/cond reactive paths now check whether
initial-result is a spread. If so, return it directly — spreads
aren't DOM nodes and can't be appended to fragments. This lets
any spread-returning component (like ~cssx/tw) work inside islands
without the spread being silently dropped.
cssx.sx: revert make-spread workaround — the root cause is now
fixed in the adapter. ~cssx/tw can use a natural top-level if.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>