phase: 20.49 COMPLETE; 20.50 Flow+String minimal reps; 20.51 selfhost v0/v1 minimal (Option A/B); hv1-inline binop/unop/copy; docs + run_all + CURRENT_TASK -> 21.0

local_tests/test_user_defined_box.hako

@@ -0,0 +1,14 @@
+box DataBox {
+    init { value }
+    
+    pack(v) {
+        me.value = v
+    }
+}
+
+static box Main {
+    main() {
+        local obj = new DataBox(42)
+        return obj.value
+    }
+}