artdag: Phase 1 DAG model + structural content addressing + 20 tests

Content-addressed node = {:op :inputs :params :commutative}; content-id is a
deterministic canonical serialization (sorted param keys; commutative ops sort
inputs). artdag/build validates dangling/cycles, topo-sorts, dedups identical
subgraphs to one id shared across DAGs. conformance.sh + scoreboard (dag 20/20).

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

lib/artdag/tests/dag.sx

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+; Phase 1 — dag model + structural content addressing.
+
+; ---- content-id determinism ----
+
+(artdag-test
+  "same spec -> same id"
+  (equal?
+    (artdag/content-id (artdag/node "blur" (list "i1") {:r 3}))
+    (artdag/content-id (artdag/node "blur" (list "i1") {:r 3})))
+  true)
+
+(artdag-test
+  "op affects id"
+  (equal?
+    (artdag/content-id (artdag/node "blur" (list "i1") {}))
+    (artdag/content-id (artdag/node "sharpen" (list "i1") {})))
+  false)
+
+(artdag-test
+  "params affect id"
+  (equal?
+    (artdag/content-id (artdag/node "blur" (list "i1") {:r 3}))
+    (artdag/content-id (artdag/node "blur" (list "i1") {:r 5})))
+  false)
+
+(artdag-test
+  "inputs affect id"
+  (equal?
+    (artdag/content-id (artdag/node "add" (list "i1") {}))
+    (artdag/content-id (artdag/node "add" (list "i2") {})))
+  false)
+
+(artdag-test
+  "param key order does not affect id"
+  (equal?
+    (artdag/content-id (artdag/node "op" (list) {:a 1 :b 2}))
+    (artdag/content-id (artdag/node "op" (list) {:a 1 :b 2})))
+  true)
+
+; ---- commutativity ----
+
+(artdag-test
+  "commutative op: input order ignored"
+  (equal?
+    (artdag/content-id (artdag/cnode "add" (list "i1" "i2") {}))
+    (artdag/content-id (artdag/cnode "add" (list "i2" "i1") {})))
+  true)
+
+(artdag-test
+  "non-commutative op: input order matters"
+  (equal?
+    (artdag/content-id (artdag/node "sub" (list "i1" "i2") {}))
+    (artdag/content-id (artdag/node "sub" (list "i2" "i1") {})))
+  false)
+
+; ---- build: success ----
+
+(artdag-test
+  "build ok for valid dag"
+  (get
+    (artdag/build
+      (list
+        (list "a" "load" (list) {})
+        (list "b" "load" (list) {:s 1})
+        (list "c" "add" (list "a" "b") {})))
+    :ok)
+  true)
+
+(artdag-test
+  "node-count counts distinct nodes"
+  (artdag/node-count
+    (artdag/build
+      (list
+        (list "a" "load" (list) {})
+        (list "b" "load" (list) {:s 1})
+        (list "c" "add" (list "a" "b") {}))))
+  3)
+
+; ---- subgraph sharing ----
+
+(artdag-test
+  "identical leaves dedup to one node"
+  (artdag/node-count
+    (artdag/build
+      (list
+        (list "a" "load" (list) {:s 1})
+        (list "b" "load" (list) {:s 1})
+        (list "c" "add" (list "a" "b") {}))))
+  2)
+
+(artdag-test
+  "duplicate names map to same id"
+  (let
+    ((d (artdag/build (list (list "a" "load" (list) {:s 1}) (list "b" "load" (list) {:s 1})))))
+    (equal? (artdag/dag-id d "a") (artdag/dag-id d "b")))
+  true)
+
+(artdag-test
+  "identical subgraph shares id across dags"
+  (let
+    ((d1 (artdag/build (list (list "x" "load" (list) {:s 7}) (list "y" "neg" (list "x") {}))))
+      (d2
+        (artdag/build
+          (list
+            (list "p" "load" (list) {:s 7})
+            (list "q" "neg" (list "p") {})))))
+    (equal? (artdag/dag-id d1 "y") (artdag/dag-id d2 "q")))
+  true)
+
+; ---- validation ----
+
+(artdag-test
+  "cycle rejected"
+  (get
+    (artdag/build
+      (list
+        (list "a" "f" (list "b") {})
+        (list "b" "g" (list "a") {})))
+    :error)
+  "cycle")
+
+(artdag-test
+  "self-cycle rejected"
+  (get (artdag/build (list (list "a" "f" (list "a") {}))) :error)
+  "cycle")
+
+(artdag-test
+  "dangling input rejected"
+  (get
+    (artdag/build (list (list "a" "f" (list "ghost") {})))
+    :error)
+  "dangling")
+
+(artdag-test
+  "dangling refs reported"
+  (get
+    (artdag/build (list (list "a" "f" (list "ghost") {})))
+    :refs)
+  (list "ghost"))
+
+; ---- topological order ----
+
+(artdag-test
+  "topo order: deps before dependents"
+  (let
+    ((d (artdag/build (list (list "c" "add" (list "a" "b") {}) (list "a" "load" (list) {:s 1}) (list "b" "load" (list) {:s 2})))))
+    (artdag/dag-order d))
+  (let
+    ((d (artdag/build (list (list "c" "add" (list "a" "b") {}) (list "a" "load" (list) {:s 1}) (list "b" "load" (list) {:s 2})))))
+    (list (artdag/dag-id d "a") (artdag/dag-id d "b") (artdag/dag-id d "c"))))
+
+(artdag-test
+  "topo order: deep chain"
+  (let
+    ((d (artdag/build (list (list "d" "f" (list "c") {}) (list "c" "f" (list "b") {}) (list "b" "f" (list "a") {}) (list "a" "load" (list) {})))))
+    (artdag/dag-order d))
+  (let
+    ((d (artdag/build (list (list "d" "f" (list "c") {}) (list "c" "f" (list "b") {}) (list "b" "f" (list "a") {}) (list "a" "load" (list) {})))))
+    (list
+      (artdag/dag-id d "a")
+      (artdag/dag-id d "b")
+      (artdag/dag-id d "c")
+      (artdag/dag-id d "d"))))
+
+; ---- accessors ----
+
+(artdag-test
+  "dag-node-by-name returns node spec"
+  (artdag/node-op
+    (artdag/dag-node-by-name
+      (artdag/build (list (list "a" "load" (list) {})))
+      "a"))
+  "load")
+
+(artdag-test
+  "resolved inputs are content-ids"
+  (let
+    ((d (artdag/build (list (list "a" "load" (list) {}) (list "b" "neg" (list "a") {})))))
+    (artdag/node-inputs (artdag/dag-node-by-name d "b")))
+  (let
+    ((d (artdag/build (list (list "a" "load" (list) {}) (list "b" "neg" (list "a") {})))))
+    (list (artdag/dag-id d "a"))))