Switch SSR from SX adapter to native Sx_render.render_to_html.
Islands that fail SSR emit <span data-sx-island="name"> placeholders
instead of recursing into client-only bodies. Eliminates the <home
symbol error cascade that made the homepage render 23s.
Performance (warm, single process):
Homepage: 131-191ms TTFB (was 202ms on Quart) — faster
Geography: 203-229ms TTFB (was 144ms on Quart) — close
Reactive: 155-290ms TTFB (was 187ms on Quart) — similar
Memory: 2MB RSS (was 570MB on Quart) — 285x reduction
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>