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/blog.sx

@@ -1,34 +1,72 @@
-;; lib/host/blog.sx — Blog domain on the host. Serves published posts as HTML at
-;; GET /<slug>/ — the original strangler target (Quart: blog/bp/post/routes.py,
-;; handler post_detail). Published posts are world-visible, so this endpoint is
-;; ANONYMOUS — no auth, visibility is trivially "visible".
+;; lib/host/blog.sx — Blog domain on the host. Posts are content-on-sx documents
+;; whose SOURCE OF TRUTH is the durable SX store (persist op-log on disk): a post
+;; is published by appending insert ops to its stream. Serving GET /<slug>/ renders
+;; the post to HTML via content/html. The original strangler target (Quart blog
+;; post_detail); published posts are world-visible, so this endpoint is ANONYMOUS.
 ;;
-;; A post is a content-on-sx document (CtDoc) rendered to HTML via the content
-;; facade (content/html). Posts live in an in-memory registry keyed by slug: this
-;; is the "prove the machinery" step — swap host/blog-lookup for a persist-backed
-;; content stream later without touching the handler or the route.
-;; Depends on lib/content/* (+ the Smalltalk + persist preloads its classes need)
-;; + lib/dream/* + lib/host/handler.sx.
+;; READ PATH — materialised view, not per-request IO. The durable backend reads
+;; via `perform` (kernel IO suspension), which is serviceable on the main thread
+;; (boot) but NOT inside an http-listen request handler thread. So posts are
+;; materialised from the store into an in-memory view at boot (and on publish),
+;; and request handlers read that view — fast, perform-free. The store stays the
+;; source of truth; the view is a cache rebuilt from it on startup.
+;; Depends on lib/content/* (+ Smalltalk + persist preloads) + lib/dream/* +
+;; lib/host/handler.sx.
 
-;; Register the content class table + render methods (idempotent). Must run before
-;; any CtDoc is built/rendered; called at module load below.
+;; Register content classes + render methods (idempotent); called at load below.
 (define host/blog-bootstrap!
   (fn () (begin (st-bootstrap-classes!) (content/bootstrap!))))
 
-;; ── in-memory post registry (slug -> CtDoc) ─────────────────────────
-(define host/blog-posts {})
-(define host/blog-register!
-  (fn (slug doc) (set! host/blog-posts (assoc host/blog-posts slug doc))))
-(define host/blog-lookup (fn (slug) (get host/blog-posts slug)))
-(define host/blog-reset! (fn () (set! host/blog-posts {})))
+;; ── store (durable source of truth) + view (in-memory serving cache) ─
+(define host/blog-store (persist/open))
+(define host/blog-view {})
+(define host/blog-use-store!
+  (fn (b) (begin (set! host/blog-store b) (set! host/blog-view {}))))
 
-;; Build a simple post doc (title heading + body paragraph). Convenience for
-;; seeding and tests; real posts arrive from the content store.
-(define host/blog-make
-  (fn (slug title body)
-    (doc-append
-      (doc-append (doc-empty slug) (mk-heading (str slug "-h") 1 title))
-      (mk-text (str slug "-body") body))))
+;; content streams are keyed "content:<slug>"; recover the slug.
+(define host/blog--stream-slug
+  (fn (stream)
+    (if (starts-with? stream "content:") (substr stream 8) nil)))
+
+;; ── publish + lookup ────────────────────────────────────────────────
+;; Publish a simple post (title heading + body paragraph): append its insert ops
+;; to the durable store, then refresh the in-memory view. `at` is a logical ts.
+(define host/blog-publish!
+  (fn (slug title body at)
+    (let ((hid (str slug "-h")) (tid (str slug "-body")))
+      (content/commit-all! host/blog-store slug
+        (list
+          (op-insert (mk-heading hid 1 title) nil)
+          (op-insert (mk-text tid body) hid))
+        at)
+      (set! host/blog-view
+        (assoc host/blog-view slug (content/head host/blog-store slug))))))
+
+;; Materialise every persisted post from the store into the view. Run at boot on
+;; the main thread (content/head performs IO, fine here, not in a request).
+(define host/blog-load-all!
+  (fn ()
+    (for-each
+      (fn (stream)
+        (let ((slug (host/blog--stream-slug stream)))
+          (when slug
+            (let ((doc (content/head host/blog-store slug)))
+              (when (> (content/count doc) 0)
+                (set! host/blog-view (assoc host/blog-view slug doc)))))))
+      (persist/backend-streams host/blog-store))))
+
+;; Idempotent seed: if the slug isn't already materialised, recover it from the
+;; store (prior run) or publish it fresh. No duplicate ops on restart.
+(define host/blog-seed!
+  (fn (slug title body at)
+    (when (nil? (get host/blog-view slug))
+      (let ((existing (content/head host/blog-store slug)))
+        (if (> (content/count existing) 0)
+          (set! host/blog-view (assoc host/blog-view slug existing))
+          (host/blog-publish! slug title body at))))))
+
+;; Lookup is pure in-memory (no perform) — safe inside a request handler.
+(define host/blog-lookup (fn (slug) (get host/blog-view slug)))
 
 ;; ── handler: GET /<slug>/ -> rendered HTML (200) or 404 ─────────────
 (define host/blog-post