host: SX-native HTML→SX converter (the radar migrator) + first-class HTML import

lib/host/htmlsx.sx — a pure-SX HTML → SX converter (char-level tokenizer + stack parser):
host/html->sx turns a post's HTML into an (article …) tree that host/blog--decompose! consumes
— img / p / figure+figcaption / iframe / headings / blockquote / lists, inline strong/em/a kept
nested (decompose flattens to text), entities decoded to UTF-8, comments+doctype skipped. This
replaces the one-off external Python converter used for the nt-live-encore import.

import-post! now accepts a raw "html" field (converted via html->sx, serialized to sx_content,
decomposed) alongside "sx_content" — so importing real Ghost HTML is first-class. Wired
htmlsx.sx into conformance.sh + serve.sh module lists (loads in conformance AND live).

New htmlsx suite 8/8 (text/entities/void/nested/figure/iframe/comments + an html→sx→decompose→
typed-cards round-trip); blog 197/197 (+ import-from-html test).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/host/serve.sh

@@ -88,6 +88,7 @@ MODULES=(
   "lib/host/relations.sx"
   "lib/host/compose.sx"
   "lib/host/execute.sx"
+  "lib/host/htmlsx.sx"
   "lib/host/blog.sx"
   "lib/host/server.sx"
 )