controllogic: add Graph.StateVars declarations (persisted via store JSON)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/controllogic/store_test.go

@@ -0,0 +1,33 @@
+package controllogic
+
+import "testing"
+
+func TestStoreRoundTripStateVars(t *testing.T) {
+	dir := t.TempDir()
+	st, err := NewStore(dir) // NewStore takes the storage DIRECTORY
+	if err != nil {
+		t.Fatal(err)
+	}
+	g := Graph{
+		ID:   "g1",
+		Name: "with-vars",
+		StateVars: []StateVar{
+			{Name: "count", Type: "number", Initial: "0"},
+			{Name: "buf", Type: "array", Initial: "[1,2]", Elem: "number", Sizing: "capped", Capacity: 5},
+		},
+	}
+	if err := st.Save(g); err != nil { // Save returns only error
+		t.Fatal(err)
+	}
+	st2, err := NewStore(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err := st2.Get("g1") // Get returns (Graph, error); ErrNotFound if absent
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got.StateVars) != 2 || got.StateVars[1].Name != "buf" || got.StateVars[1].Capacity != 5 {
+		t.Fatalf("statevars not round-tripped: %#v", got.StateVars)
+	}
+}