host: Phase 1 — router + handler + GET /feed endpoint on Dream, 28/28

First migrated endpoint onto the SX host. lib/host is a thin wiring layer:
a host handler is a Dream handler (request->response) that calls a subsystem
public API and serialises via a shared JSON envelope.

- handler.sx: host/ok, host/ok-status, host/error, host/json-status (Dream's
  dream-json is 200-only), host/query-int
- router.sx: host/make-app assembles per-domain route groups + /health probe
  into one dream-router (reuses dr/flatten-routes)
- feed.sx: GET /feed reads feed/all + stream combinators, recent-first, with
  ?actor= filter and ?limit= cap
- 3 test suites incl. a golden test (body == subsystem recent stream + envelope)
- conformance.sh mirrors lib/dream's runner

Builds on dream-on-sx (merged, gate green 480/480) rather than a throwaway
native request model; collapses most of plan Phase 4 into Phase 1.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/host/tests/feed.sx

@@ -0,0 +1,98 @@
+;; lib/host/tests/feed.sx — the first migrated endpoint, GET /feed. Includes a
+;; golden test: the host response body must equal the feed subsystem's own
+;; recent-first stream wrapped in the standard envelope — the endpoint adds the
+;; HTTP/JSON shell and nothing else.
+
+(define host-fd-pass 0)
+(define host-fd-fail 0)
+(define host-fd-fails (list))
+
+(define
+  host-fd-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! host-fd-pass (+ host-fd-pass 1))
+      (begin
+        (set! host-fd-fail (+ host-fd-fail 1))
+        (append! host-fd-fails {:name name :actual actual :expected expected})))))
+
+(define
+  host-fd-req
+  (fn (target) (dream-request "GET" target {} "")))
+
+(define
+  host-fd-app
+  (host/make-app (list host/feed-routes)))
+
+;; ── empty feed ─────────────────────────────────────────────────────
+(feed/reset!)
+(host-fd-test
+  "empty feed 200"
+  (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\":[]")
+  true)
+
+;; ── seeded feed ────────────────────────────────────────────────────
+(feed/reset!)
+(feed/post {:actor "alice" :verb "post" :object "p1" :at 1})
+(feed/post {:actor "bob" :verb "post" :object "p2" :at 2})
+(feed/post {:actor "alice" :verb "like" :object "p2" :at 3})
+
+;; recent-first: newest activity (at 3) leads, so its object p2 appears before p1.
+(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")))
+  true)
+
+;; actor filter: only alice's two activities.
+(host-fd-test
+  "actor filter count"
+  (feed/count
+    (feed/by-actor (feed/recent (feed/all)) "alice"))
+  2)
+(host-fd-test
+  "actor filter excludes bob"
+  (contains?
+    (dream-resp-body (host-fd-app (host-fd-req "/feed?actor=alice")))
+    "bob")
+  false)
+
+;; limit: cap to a single activity (the most recent).
+(host-fd-test
+  "limit caps results"
+  (contains?
+    (dream-resp-body (host-fd-app (host-fd-req "/feed?limit=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))))
+    "}"))
+(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")))
+    "}"))
+
+(define
+  host-fd-tests-run!
+  (fn
+    ()
+    {:total (+ host-fd-pass host-fd-fail)
+     :passed host-fd-pass
+     :failed host-fd-fail
+     :fails host-fd-fails}))

lib/host/tests/handler.sx

@@ -0,0 +1,86 @@
+;; lib/host/tests/handler.sx — host JSON envelope + request-reading helpers.
+
+(define host-hd-pass 0)
+(define host-hd-fail 0)
+(define host-hd-fails (list))
+
+(define
+  host-hd-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! host-hd-pass (+ host-hd-pass 1))
+      (begin
+        (set! host-hd-fail (+ host-hd-fail 1))
+        (append! host-hd-fails {:name name :actual actual :expected expected})))))
+
+;; ── host/ok ────────────────────────────────────────────────────────
+(host-hd-test "ok status 200" (dream-status (host/ok "x")) 200)
+(host-hd-test
+  "ok content-type json"
+  (dream-resp-header (host/ok "x") "content-type")
+  "application/json")
+(host-hd-test
+  "ok envelope ok:true"
+  (contains? (dream-resp-body (host/ok "x")) "\"ok\":true")
+  true)
+(host-hd-test
+  "ok envelope carries data"
+  (contains? (dream-resp-body (host/ok "hi")) "\"data\":\"hi\"")
+  true)
+
+;; ── host/ok-status ─────────────────────────────────────────────────
+(host-hd-test "ok-status custom" (dream-status (host/ok-status 201 "y")) 201)
+(host-hd-test
+  "ok-status data"
+  (contains? (dream-resp-body (host/ok-status 201 "y")) "\"data\":\"y\"")
+  true)
+
+;; ── host/error ─────────────────────────────────────────────────────
+(host-hd-test "error status" (dream-status (host/error 404 "nope")) 404)
+(host-hd-test
+  "error ok:false"
+  (contains? (dream-resp-body (host/error 404 "nope")) "\"ok\":false")
+  true)
+(host-hd-test
+  "error message"
+  (contains? (dream-resp-body (host/error 404 "nope")) "\"error\":\"nope\"")
+  true)
+(host-hd-test
+  "error content-type json"
+  (dream-resp-header (host/error 500 "boom") "content-type")
+  "application/json")
+
+;; ── host/json-status ───────────────────────────────────────────────
+(host-hd-test
+  "json-status arbitrary status"
+  (dream-status (host/json-status 418 {:a 1}))
+  418)
+(host-hd-test
+  "json-status encodes body"
+  (contains? (dream-resp-body (host/json-status 200 {:a 1})) "\"a\":1")
+  true)
+
+;; ── host/query-int ─────────────────────────────────────────────────
+(define
+  host-hd-req
+  (fn (target) (dream-request "GET" target {} "")))
+
+(host-hd-test
+  "query-int present"
+  (host/query-int (host-hd-req "/x?limit=5") "limit" 10)
+  5)
+(host-hd-test
+  "query-int absent -> fallback"
+  (host/query-int (host-hd-req "/x") "limit" 10)
+  10)
+
+(define
+  host-hd-tests-run!
+  (fn
+    ()
+    {:total (+ host-hd-pass host-hd-fail)
+     :passed host-hd-pass
+     :failed host-hd-fail
+     :fails host-hd-fails}))

lib/host/tests/router.sx

@@ -0,0 +1,75 @@
+;; lib/host/tests/router.sx — host app assembly: health endpoint, group mounting,
+;; 404 fallback.
+
+(define host-rt-pass 0)
+(define host-rt-fail 0)
+(define host-rt-fails (list))
+
+(define
+  host-rt-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! host-rt-pass (+ host-rt-pass 1))
+      (begin
+        (set! host-rt-fail (+ host-rt-fail 1))
+        (append! host-rt-fails {:name name :actual actual :expected expected})))))
+
+(define
+  host-rt-req
+  (fn (method target) (dream-request method target {} "")))
+
+;; An app built from one domain group of two routes.
+(define
+  host-rt-app
+  (host/make-app
+    (list
+      (list
+        (dream-get "/ping" (fn (req) (host/ok "pong")))
+        (dream-get "/widgets/:id" (fn (req) (host/ok (dream-param req "id"))))))))
+
+;; ── health ─────────────────────────────────────────────────────────
+(host-rt-test
+  "health status 200"
+  (dream-status (host-rt-app (host-rt-req "GET" "/health")))
+  200)
+(host-rt-test
+  "health body healthy"
+  (contains?
+    (dream-resp-body (host-rt-app (host-rt-req "GET" "/health")))
+    "healthy")
+  true)
+
+;; ── group routes mounted ───────────────────────────────────────────
+(host-rt-test
+  "group route ping"
+  (contains?
+    (dream-resp-body (host-rt-app (host-rt-req "GET" "/ping")))
+    "pong")
+  true)
+(host-rt-test
+  "group path param"
+  (contains?
+    (dream-resp-body (host-rt-app (host-rt-req "GET" "/widgets/42")))
+    "\"data\":\"42\"")
+  true)
+
+;; ── fallback ───────────────────────────────────────────────────────
+(host-rt-test
+  "unknown path 404"
+  (dream-status (host-rt-app (host-rt-req "GET" "/nope")))
+  404)
+(host-rt-test
+  "wrong method 405"
+  (dream-status (host-rt-app (host-rt-req "POST" "/ping")))
+  405)
+
+(define
+  host-rt-tests-run!
+  (fn
+    ()
+    {:total (+ host-rt-pass host-rt-fail)
+     :passed host-rt-pass
+     :failed host-rt-fail
+     :fails host-rt-fails}))