HS: fetch JSON unwrap (+4 tests)

Adds hs-host-to-sx to convert raw host-handle JS objects/arrays returned by
json-parse or io-fetch into proper SX dicts/lists. hs-fetch now calls it on
the result when format is "json". Detects host handles via absence of the
internal `_type` marker, then walks Object.keys / Array items recursively.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

shared/static/wasm/sx/hs-runtime.sx

@@ -687,14 +687,70 @@
           (dom-insert-adjacent-html target "beforeend" (str value)))
         (true nil)))))
 ;; Property-based is — check obj.key truthiness
+(define
+  hs-host-to-sx
+  (fn
+    (v)
+    (cond
+      ((nil? v) v)
+      ((number? v) v)
+      ((string? v) v)
+      ((boolean? v) v)
+      (true
+        (let
+          ((marker (host-get v "_type")))
+          (cond
+            ((= marker "dict")
+              (let
+                ((out (dict)))
+                (begin
+                  (for-each
+                    (fn (k) (dict-set! out k (hs-host-to-sx (get v k))))
+                    (keys v))
+                  out)))
+            ((= marker "list") (map hs-host-to-sx v))
+            (true
+              (let
+                ((is-array (host-call (host-global "Array") "isArray" v)))
+                (if
+                  is-array
+                  (let
+                    ((len (host-get v "length")) (out (list)))
+                    (begin
+                      (let
+                        ((i 0))
+                        (for-each
+                          (fn
+                            (_)
+                            (begin
+                              (set!
+                                out
+                                (append
+                                  out
+                                  (list (hs-host-to-sx (host-get v i)))))
+                              (set! i (+ i 1))))
+                          (range 0 len)))
+                      out))
+                  (let
+                    ((out (dict)))
+                    (begin
+                      (for-each
+                        (fn
+                          (k)
+                          (dict-set! out k (hs-host-to-sx (host-get v k))))
+                        (host-call (host-global "Object") "keys" v))
+                      out)))))))))))
+;; Array slicing (inclusive both ends)
 (define
   hs-fetch
   (fn
     (url format)
     (let
-      ((fmt (cond ((nil? format) "text") ((or (= format "JSON") (= format "json") (= format "Object") (= format "object")) "json") ((or (= format "HTML") (= format "html")) "html") ((or (= format "Response") (= format "response")) "response") ((or (= format "Text") (= format "text")) "text") (true format))))
-      (perform (list "io-fetch" url fmt)))))
-;; Array slicing (inclusive both ends)
+      ((fmt (cond ((nil? format) "text") ((or (= format "json") (= format "JSON") (= format "Object")) "json") ((or (= format "html") (= format "HTML")) "html") ((or (= format "response") (= format "Response")) "response") ((or (= format "text") (= format "Text")) "text") (true format))))
+      (let
+        ((raw (perform (list "io-fetch" url fmt))))
+        (cond ((= fmt "json") (hs-host-to-sx raw)) (true raw))))))
+;; Collection: sorted by
 (define
   hs-json-escape
   (fn
@@ -725,7 +781,7 @@
         (walk)
         out)
       "\"")))
-;; Collection: sorted by
+;; Collection: sorted by descending
 (define
   hs-json-stringify
   (fn
@@ -749,7 +805,7 @@
               (keys v)))
           "}"))
       (true (hs-json-escape (str v))))))
-;; Collection: sorted by descending
+;; Collection: split by
 (define
   hs-coerce
   (fn
@@ -856,7 +912,7 @@
           (map (fn (k) (list k (get value k))) (keys value))
           value))
       (true value))))
-;; Collection: split by
+;; Collection: joined by
 (define
   hs-gather-form-nodes
   (fn
@@ -890,7 +946,7 @@
                       (each 0)))))))))
       (walk root)
       acc)))
-;; Collection: joined by
+
 (define
   hs-values-from-nodes
   (fn (nodes) (reduce hs-values-absorb (dict) nodes)))