New render_to_buf / render_to_html_streaming in sx_render.ml — writes
HTML directly to a Buffer.t instead of building intermediate strings.
Eliminates hundreds of string concatenations per page render.
Full parallel renderer: render_to_buf, render_element_buf,
render_component_buf, render_cond_buf, render_let_buf, render_map_buf,
render_for_each_buf — all buffer-native.
HTTP server SSR + shell now use streaming renderer.
Performance (warm, 2 worker domains, 2MB RSS):
Homepage: 138-195ms TTFB (Quart: 202ms) — faster
Geography: 218-286ms TTFB (Quart: 144ms)
Throughput: 6.85 req/s at c=5 (Quart: 6.8 req/s) — matched
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>