Add typed artifact codec foundation

internal/framework/contracts/artifact_test.go

@@ -0,0 +1,45 @@
+package contracts
+
+import "testing"
+
+func TestDigestArtifactSchemaUsesExactBytes(t *testing.T) {
+	first := ArtifactSchema{JSONSchema: []byte(`{"type":"object"}`)}
+	second := ArtifactSchema{JSONSchema: []byte("{\n  \"type\": \"object\"\n}")}
+
+	if got := DigestArtifactSchema(first); got != "sha256:a2c799262a3ce3c19ef5cdd983bf3d12b43ab3c426227091b909dcb7054738c0" {
+		t.Fatalf("DigestArtifactSchema() = %q, want stable SHA-256", got)
+	}
+	if DigestArtifactSchema(first) == DigestArtifactSchema(second) {
+		t.Fatal("schema digests match for different exact bytes")
+	}
+}
+
+func TestArtifactCloneHelpersOwnSlicesAndMaps(t *testing.T) {
+	schema := ArtifactSchema{ID: "notes.v1", Name: "notes", Version: "v1", JSONSchema: []byte(`{"type":"object"}`)}
+	artifact := SerializedArtifact{
+		Kind:      "test/notes",
+		Schema:    schema,
+		MediaType: "application/json",
+		Content:   []byte(`{"items":["one"]}`),
+		Metadata:  map[string]any{"origin": "test"},
+	}
+
+	clonedSchema := CloneArtifactSchema(schema)
+	cloned := CloneSerializedArtifact(artifact)
+	schema.JSONSchema[0] = '['
+	artifact.Content[0] = '['
+	artifact.Metadata["origin"] = "changed"
+
+	if string(clonedSchema.JSONSchema) != `{"type":"object"}` {
+		t.Fatalf("cloned schema = %q, want original bytes", clonedSchema.JSONSchema)
+	}
+	if string(cloned.Schema.JSONSchema) != `{"type":"object"}` {
+		t.Fatalf("serialized artifact schema = %q, want original bytes", cloned.Schema.JSONSchema)
+	}
+	if string(cloned.Content) != `{"items":["one"]}` {
+		t.Fatalf("cloned content = %q, want original bytes", cloned.Content)
+	}
+	if cloned.Metadata["origin"] != "test" {
+		t.Fatalf("cloned metadata = %#v, want independent map", cloned.Metadata)
+	}
+}