host: SX-native wire — reads + write bodies are text/sx, JSON CRUD deleted

Greenfield SX-native pivot (NOT a strangler): the host speaks SX/SXTP end to end;
JSON only at the future ActivityPub federation edge.

- OUTPUT: host/json-status -> host/sx-status — every host/ok/host/error response is
  text/sx via the serialize primitive (NOT application/json). Flips feed, relations,
  blog reads. Tests assert the SX envelope ({:ok true :data ...}).
- DELETE the blog JSON CRUD /posts (POST/PUT/DELETE) + bearer-based host/blog--protect:
  a pure old-contract REST mirror. Create/edit go through the HTML editor forms;
  programmatic writes speak SXTP. FOLLOW-UP: no browser delete route yet (was JSON-only,
  no UI) — add POST /:slug/delete + cascade edge cleanup when the metamodel UI needs it.
- INPUT: host/sx-body (sxtp.sx) parses a text/sx request body to a string-keyed dict
  (parse-safe + sxtp/-normalize). feed POST + relations attach/detach read it.
- UNIFIED field reader host/fields / host/field: text/sx body OR urlencoded form by
  content-type. The blog form handlers (new/edit/relate/unrelate) + login read through
  it — additive, urlencoded still works (no-engine / bootstrap fallback).

Conformance 290/290 (11 suites). Retires the strangler framing in the plan; adds the
'SX all the way out' wire table. The engine half (browser posts text/sx) follows.

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

lib/host/tests/feed.sx

@@ -33,8 +33,8 @@
   (dream-status (host-fd-app (host-fd-req "/feed")))
   200)
 (host-fd-test
-  "empty feed data:[]"
-  (contains? (dream-resp-body (host-fd-app (host-fd-req "/feed"))) "\"data\":[]")
+  "empty feed data ()"
+  (contains? (dream-resp-body (host-fd-app (host-fd-req "/feed"))) ":data ()")
   true)
 
 ;; ── seeded feed ────────────────────────────────────────────────────
@@ -47,7 +47,7 @@
 (host-fd-test
   "timeline recent-first"
   (let ((body (dream-resp-body (host-fd-app (host-fd-req "/feed")))))
-    (< (index-of body "\"at\":3") (index-of body "\"at\":1")))
+    (< (index-of body ":at 3") (index-of body ":at 1")))
   true)
 
 ;; actor filter: only alice's two activities.
@@ -68,25 +68,18 @@
   "limit caps results"
   (contains?
     (dream-resp-body (host-fd-app (host-fd-req "/feed?limit=1")))
-    "\"at\":1")
+    ":at 1")
   false)
 
 ;; ── golden: endpoint = subsystem recent stream + envelope ───────────
 (host-fd-test
   "golden full timeline"
   (dream-resp-body (host-fd-app (host-fd-req "/feed")))
-  (str
-    "{\"ok\":true,\"data\":"
-    (dream-json-encode (feed/items (feed/recent (feed/all))))
-    "}"))
+  (serialize {:ok true :data (feed/items (feed/recent (feed/all)))}))
 (host-fd-test
   "golden actor-filtered"
   (dream-resp-body (host-fd-app (host-fd-req "/feed?actor=alice")))
-  (str
-    "{\"ok\":true,\"data\":"
-    (dream-json-encode
-      (feed/items (feed/by-actor (feed/recent (feed/all)) "alice")))
-    "}"))
+  (serialize {:ok true :data (feed/items (feed/by-actor (feed/recent (feed/all)) "alice"))}))
 
 ;; ── write: POST /feed (auth + ACL + action) ────────────────────────
 (acl/load! (list (acl-grant "alice" "post" "feed")))
@@ -115,7 +108,7 @@
     (host-fd-wapp
       (host-fd-post
         "Bearer good"
-        "{\"actor\":\"alice\",\"verb\":\"post\",\"object\":\"p9\",\"at\":9}")))
+        "{:actor \"alice\" :verb \"post\" :object \"p9\" :at 9}")))
   201)
 (host-fd-test "post grew feed" (feed/size) 1)
 (host-fd-test
@@ -126,7 +119,7 @@
   true)
 (host-fd-test
   "post non-object body -> 400"
-  (dream-status (host-fd-wapp (host-fd-post "Bearer good" "[1,2]")))
+  (dream-status (host-fd-wapp (host-fd-post "Bearer good" "(1 2)")))
   400)
 
 (define