host: blog persisted in durable SX store + materialised view, 158/158

Blog posts now live in the durable SX store (persist/durable-backend, on-disk
under $SX_PERSIST_DIR — already built: sx_persist_store.ml + lib/persist/
durable.sx). Publishing appends insert ops to the slug's content stream; posts
survive restarts (verified: seq/log stable across container restart, re-seed
idempotent).

Read path: http-listen handlers can't drive per-request perform/IO (sx_call
doesn't resolve the CEK IO suspension the way the main loop does), so posts are
materialised from the store into an in-memory view at boot (host/blog-load-all!
+ host/blog-seed!) and request handlers read the view — perform-free. Store is
source of truth; view is a boot-rebuilt cache.

Deploy: docker-compose.dev-sx-host.yml mounts /root/sx-host-persist (chowned to
appuser 10001) at /data/persist; SX_PERSIST_DIR set. blog.rose-ash.com/welcome/
live. Per-request-IO kernel fix tracked in the plan as the next task.

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

lib/host/tests/blog.sx

@@ -22,9 +22,9 @@
 (define host-bl-app
   (host/make-app (list host/feed-routes host/blog-routes)))
 
-;; ── render a registered post ────────────────────────────────────────
-(host/blog-reset!)
-(host/blog-register! "welcome" (host/blog-make "welcome" "Hello SX" "Served by lib/host."))
+;; ── publish a post to a fresh in-memory store (hermetic) ────────────
+(host/blog-use-store! (persist/open))
+(host/blog-publish! "welcome" "Hello SX" "Served by lib/host." 1)
 
 (host-bl-test
   "post 200"
@@ -48,11 +48,17 @@
   (dream-status (host-bl-app (host-bl-req "/welcome")))
   200)
 
-;; golden: endpoint body == content facade render of the same doc
+;; golden: endpoint body == the exact rendered HTML of the published post
 (host-bl-test
-  "golden = content/html"
+  "golden render"
   (dream-resp-body (host-bl-app (host-bl-req "/welcome/")))
-  (content/html (host/blog-make "welcome" "Hello SX" "Served by lib/host.")))
+  "<h1>Hello SX</h1><p>Served by lib/host.</p>")
+
+;; persistence: a post materialises from the op-log (replay), and re-seeding is
+;; idempotent (no duplicate blocks appended).
+(host-bl-test "lookup materialises 2 blocks" (content/count (host/blog-lookup "welcome")) 2)
+(host/blog-seed! "welcome" "Hello SX" "Served by lib/host." 2)
+(host-bl-test "re-seed is idempotent" (content/count (host/blog-lookup "welcome")) 2)
 
 ;; ── unknown slug -> 404 ─────────────────────────────────────────────
 (host-bl-test