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_array_state_issue.hako

@@ -0,0 +1,11 @@
+// 🚨 ArrayBox状態保持問題のテスト
+static box Main {
+    init { result }
+    main() {
+        local arr
+        arr = new ArrayBox()
+        arr.push("hello")     // 状態変更
+        me.result = arr.length()  // 期待値: 1, 実際: 0?
+        return me.result
+    }
+}