host: Phase 3 — relations READ cut-over (get-children/get-parents), 121/121

Migrate the two internal relations read queries onto lib/relations: GET
/internal/data/get-children + /get-parents dispatch to relations/children
and relations/parents. Bridge the Quart (type,id) node key to a graph atom
symbol "type:id" with relation-type as the edge kind; optional child/parent
-type params filter by "type:" prefix. Golden tests pin each endpoint to
subsystem-call + envelope. Ledger entries flipped to :migrated (off-Quart
coverage 27% -> 45%).

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

lib/host/tests/ledger.sx

@@ -37,11 +37,15 @@
   (get (host/ledger-find host/ledger "POST" "/feed") :handler)
   "host/feed-create")
 (host-lg-test "find missing -> nil" (host/ledger-find host/ledger "GET" "/nope") nil)
+(host-lg-test
+  "find migrated relations read -> handler"
+  (get (host/ledger-find host/ledger "GET" "/internal/data/get-children") :handler)
+  "host/relations-children")
 
 ;; ── status queries ──────────────────────────────────────────────────
-(host-lg-test "migrated count" (len (host/ledger-migrated host/ledger)) 2)
+(host-lg-test "migrated count" (len (host/ledger-migrated host/ledger)) 4)
 (host-lg-test "native count" (len (host/ledger-native host/ledger)) 1)
-(host-lg-test "proxied count" (len (host/ledger-proxied host/ledger)) 8)
+(host-lg-test "proxied count" (len (host/ledger-proxied host/ledger)) 6)
 
 ;; ── served? predicate ───────────────────────────────────────────────
 (host-lg-test
@@ -73,11 +77,11 @@
 ;; ── coverage ────────────────────────────────────────────────────────
 (define host-lg-cov (host/ledger-coverage host/ledger))
 (host-lg-test "coverage total" (get host-lg-cov :total) 11)
-(host-lg-test "coverage migrated" (get host-lg-cov :migrated) 2)
-(host-lg-test "coverage proxied" (get host-lg-cov :proxied) 8)
+(host-lg-test "coverage migrated" (get host-lg-cov :migrated) 4)
+(host-lg-test "coverage proxied" (get host-lg-cov :proxied) 6)
 (host-lg-test "coverage native" (get host-lg-cov :native) 1)
-(host-lg-test "coverage served" (get host-lg-cov :served) 3)
-(host-lg-test "coverage percent" (get host-lg-cov :percent) 27)
+(host-lg-test "coverage served" (get host-lg-cov :served) 5)
+(host-lg-test "coverage percent" (get host-lg-cov :percent) 45)
 
 (define
   host-lg-tests-run!

lib/host/tests/relations.sx

@@ -0,0 +1,112 @@
+;; lib/host/tests/relations.sx — the migrated relations read endpoints,
+;; GET /internal/data/get-children and /get-parents, dispatching to lib/relations.
+;; Golden tests pin each endpoint to "subsystem call + standard envelope": the
+;; host adds the HTTP/JSON shell over relations/children|parents and nothing else
+;; (golden derived from the same subsystem call, so result order matches).
+
+(define host-rl-pass 0)
+(define host-rl-fail 0)
+(define host-rl-fails (list))
+
+(define
+  host-rl-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! host-rl-pass (+ host-rl-pass 1))
+      (begin
+        (set! host-rl-fail (+ host-rl-fail 1))
+        (append! host-rl-fails {:name name :actual actual :expected expected})))))
+
+(define host-rl-req (fn (target) (dream-request "GET" target {} "")))
+(define host-rl-app (host/make-app (list host/relations-routes)))
+(define host-rl-sym (fn (s) (string->symbol s)))
+
+;; ── seed a known graph ──────────────────────────────────────────────
+;; org:1 --member--> list:7, list:8 ; org:1 --owner--> page:9
+(relations/load! (list))
+(relations/relate (host-rl-sym "org:1") (host-rl-sym "list:7") (host-rl-sym "member"))
+(relations/relate (host-rl-sym "org:1") (host-rl-sym "list:8") (host-rl-sym "member"))
+(relations/relate (host-rl-sym "org:1") (host-rl-sym "page:9") (host-rl-sym "owner"))
+
+;; ── get-children ────────────────────────────────────────────────────
+(define host-rl-kids
+  "/internal/data/get-children?parent-type=org&parent-id=1&relation-type=member")
+(host-rl-test "children 200" (dream-status (host-rl-app (host-rl-req host-rl-kids))) 200)
+(host-rl-test
+  "children has list:7"
+  (contains? (dream-resp-body (host-rl-app (host-rl-req host-rl-kids))) "list:7")
+  true)
+(host-rl-test
+  "children has list:8"
+  (contains? (dream-resp-body (host-rl-app (host-rl-req host-rl-kids))) "list:8")
+  true)
+(host-rl-test
+  "children excludes other-kind page:9"
+  (contains? (dream-resp-body (host-rl-app (host-rl-req host-rl-kids))) "page:9")
+  false)
+(host-rl-test
+  "children count via subsystem"
+  (len (relations/children (host-rl-sym "org:1") (host-rl-sym "member")))
+  2)
+
+;; child-type filter narrows by node prefix.
+(host-rl-test
+  "children child-type=list keeps both"
+  (contains?
+    (dream-resp-body (host-rl-app (host-rl-req (str host-rl-kids "&child-type=list"))))
+    "list:8")
+  true)
+(host-rl-test
+  "children child-type=page filters all out"
+  (contains?
+    (dream-resp-body (host-rl-app (host-rl-req (str host-rl-kids "&child-type=page"))))
+    "list:7")
+  false)
+
+;; ── get-parents ─────────────────────────────────────────────────────
+(define host-rl-par
+  "/internal/data/get-parents?child-type=list&child-id=7&relation-type=member")
+(host-rl-test "parents 200" (dream-status (host-rl-app (host-rl-req host-rl-par))) 200)
+(host-rl-test
+  "parents has org:1"
+  (contains? (dream-resp-body (host-rl-app (host-rl-req host-rl-par))) "org:1")
+  true)
+
+;; ── missing required params -> 400 ──────────────────────────────────
+(host-rl-test
+  "children missing param -> 400"
+  (dream-status (host-rl-app (host-rl-req "/internal/data/get-children?parent-type=org")))
+  400)
+(host-rl-test
+  "parents missing param -> 400"
+  (dream-status (host-rl-app (host-rl-req "/internal/data/get-parents?child-type=list")))
+  400)
+
+;; ── golden: endpoint = subsystem call + envelope ────────────────────
+(host-rl-test
+  "golden children"
+  (dream-resp-body (host-rl-app (host-rl-req host-rl-kids)))
+  (str
+    "{\"ok\":true,\"data\":"
+    (dream-json-encode
+      (host/-rel-strings (relations/children (host-rl-sym "org:1") (host-rl-sym "member"))))
+    "}"))
+(host-rl-test
+  "golden parents"
+  (dream-resp-body (host-rl-app (host-rl-req host-rl-par)))
+  (str
+    "{\"ok\":true,\"data\":"
+    (dream-json-encode
+      (host/-rel-strings (relations/parents (host-rl-sym "list:7") (host-rl-sym "member"))))
+    "}"))
+
+(define
+  host-rl-tests-run!
+  (fn
+    ()
+    {:total (+ host-rl-pass host-rl-fail)
+     :passed host-rl-pass
+     :failed host-rl-fail
+     :fails host-rl-fails}))