host: blog on the editor's sx_content model + render-to-html, 171/171

Pivot blog to the SX editor's content model. The editor (blog/sx/editor.sx)
emits sx_content = SX element markup, NOT content-on-sx CtDoc blocks. So a post
is now a {slug,title,sx_content,status} record in the durable persist KV, and a
post page is render-to-html(parse sx_content) — server-side, static, no client
runtime needed to view.

Endpoints: GET / (HTML index), /<slug>/ (rendered post), /posts (JSON list),
/new (create form); POST /new (form-urlencoded editor ingest, slug from title,
303 redirect), POST /posts (JSON create), PUT/DELETE /posts/<slug>. Writes
behind auth+ACL (edit/blog). Dropped the content-on-sx/Smalltalk preload chain;
added spec/render + web/adapter-html (render-to-html) + lib/dream/form.

BONUS: render-to-html is ~0ms (vs the 2s content-on-sx Smalltalk asHTML) — it
doesn't hit the JIT-miscompiled path, so blog rendering is no longer slow.

Live: blog.rose-ash.com/ lists posts, /welcome/ renders instantly. Reads live;
the form-ingest write path needs an auth decision before going live (browser
forms can't send bearer; needs session or a Caddy basicauth gate).

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

plans/host-on-sx.md

@@ -36,10 +36,15 @@ host — no `ocaml-on-sx` dependency.
 
 ## Status (rolling)
 
-`bash lib/host/conformance.sh` → **158/158** (9 suites: handler, middleware, sxtp,
-router, feed, relations, blog, server, ledger). Blog posts now persist in the
-durable SX store (`persist/durable-backend`, on-disk under `$SX_PERSIST_DIR`),
-materialised into an in-memory view at boot and served from there.
+`bash lib/host/conformance.sh` → **171/171** (9 suites: handler, middleware, sxtp,
+router, feed, relations, blog, server, ledger). **Blog now runs on the EDITOR's
+content model** (`sx_content` = SX element markup, what `blog/sx/editor.sx`
+emits), NOT content-on-sx CtDoc: a post is a `{slug,title,sx_content,status}`
+record in the durable persist **KV**, and a post page is `render-to-html (parse
+sx_content)`. Full CRUD + an editor form-ingest endpoint (`POST /new`,
+form-urlencoded) + JSON API, writes auth+ACL guarded. **`render-to-html` is fast
+(~0ms)** — it doesn't hit the JIT-miscompiled Smalltalk path, so blog rendering
+is no longer the 2s problem (that was content-on-sx's `asHTML`).
 
 > **Per-request IO (kernel) — FIXED.** `http-listen` handlers used to run via
 > `Sx_runtime.sx_call` (bare CEK, no IO resolution), so a handler doing a durable