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>

docker-compose.dev-sx-host.yml

@@ -20,6 +20,8 @@ services:
       HOST_PORT: "8000"
       # Bind all interfaces so Caddy (on externalnet) can reach it.
       SX_HTTP_HOST: "0.0.0.0"
+      # Durable persist store root — on a named volume so data survives restarts.
+      SX_PERSIST_DIR: /data/persist
       OCAMLRUNPARAM: "b"
     volumes:
       # SX source (hot-reload on container restart)
@@ -27,6 +29,10 @@ services:
       - ./lib:/app/lib:ro
       # OCaml server binary — this worktree's build (has the SX_HTTP_HOST bind fix)
       - ./hosts/ocaml/_build/default/bin/sx_server.exe:/app/bin/sx_server:ro
+      # Durable persist store (the SX op-log/kv on disk) — survives restarts.
+      # Host dir, chowned to the image's appuser (uid 10001) so the non-root
+      # server can write: sudo mkdir -p /root/sx-host-persist && sudo chown 10001:10001 /root/sx-host-persist
+      - /root/sx-host-persist:/data/persist
     networks:
       - externalnet
       - default