artdag: DAG wire serialization — portable record form + integrity + 13 tests

serialize.sx emits a topo-ordered (id op inputs params commutative) record list
that survives write/read (string-keyed node dicts do not; empty inputs read back
as nil and are normalized). wire->dag reconstructs a runnable dag by content-id;
wire-verify recomputes ids to reject tampering. dag->string/string->dag for text
transport. serialize 13/13, total 128/128.

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

lib/artdag/serialize.sx

@@ -0,0 +1,62 @@
+; lib/artdag/serialize.sx — portable wire form for whole DAGs, so a peer can
+; receive and run a graph it did not author. The form is a topo-ordered list of
+; node records (id op inputs params commutative) — plain lists with keyword-keyed
+; param dicts, which survive write/read (unlike string-keyed node dicts). The id
+; is the content-id, so the form is self-verifying. Depends on dag.sx.
+
+(define
+  artdag/node->record
+  (fn
+    (dag id)
+    (let
+      ((n (artdag/dag-get dag id)))
+      (list
+        id
+        (artdag/node-op n)
+        (artdag/node-inputs n)
+        (artdag/node-params n)
+        (get n :commutative)))))
+
+; dag -> list of records, in topological order.
+(define
+  artdag/dag->wire
+  (fn
+    (dag)
+    (map (fn (id) (artdag/node->record dag id)) (artdag/dag-order dag))))
+
+; an empty input list reads back as nil; normalize it.
+(define
+  artdag/-rec-inputs
+  (fn (rec) (let ((i (nth rec 2))) (if (nil? i) (list) i))))
+
+(define artdag/-rec->node (fn (rec) {:inputs (artdag/-rec-inputs rec) :commutative (nth rec 4) :op (nth rec 1) :params (nth rec 3)}))
+
+; records -> dag. Local author names are not part of the wire form; the receiver
+; works by content-id. :names is left empty.
+(define
+  artdag/wire->dag
+  (fn
+    (records)
+    (reduce
+      (fn (dag rec) (let ((id (nth rec 0))) {:names (get dag :names) :order (concat (get dag :order) (list id)) :ok true :nodes (assoc (get dag :nodes) id (artdag/-rec->node rec))}))
+      {:names {} :order (list) :ok true :nodes {}}
+      records)))
+
+; integrity: each record's id must equal the content-id recomputed from its spec.
+(define
+  artdag/wire-verify
+  (fn
+    (records)
+    (every?
+      (fn
+        (rec)
+        (= (nth rec 0) (artdag/content-id (artdag/-rec->node rec))))
+      records)))
+
+; string transport.
+(define
+  artdag/dag->string
+  (fn (dag) (write-to-string (artdag/dag->wire dag))))
+(define
+  artdag/string->dag
+  (fn (s) (artdag/wire->dag (read (open-input-string s)))))