host: experimental unguarded create-only POST /new — editor publishes live, 173/173

host/blog-open-create-routes mounts POST /new with error-trapping but NO auth
(create-only; no PUT/DELETE), so the SX editor can publish to the host
end-to-end on the experimental subdomain. VALIDATED LIVE: editor-style
form-urlencoded POST -> 303 -> post renders at /<slug>/ and lists on /.

Deliberate short-lived public write hole (create-only, obscure subdomain).
MUST be gated before real use: Caddy basicauth on /new, or session auth.
Swap host/blog-open-create-routes -> host/blog-write-routes <resolver> to gate.

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

lib/host/tests/blog.sx

@@ -124,6 +124,17 @@
   (dream-status (host-bl-wapp (host-bl-send "DELETE" "/posts/ghost" "Bearer good" "" "")))
   404)
 
+;; -- experimental unguarded create-only route (POST /new, no auth) --
+(define host-bl-oapp (host/make-app (list host/blog-open-create-routes host/blog-routes)))
+(host/blog-use-store! (persist/open))
+(host-bl-test "open create no auth -> 303"
+  (dream-status (host-bl-oapp (host-bl-send "POST" "/new" nil
+    "application/x-www-form-urlencoded" "title=Open+Post&sx_content=(p+%22o%22)&status=published")))
+  303)
+(host-bl-test "open-created post renders"
+  (contains? (dream-resp-body (host-bl-oapp (host-bl-req "/open-post/"))) "<p>o</p>")
+  true)
+
 (define
   host-bl-tests-run!
   (fn ()