docs: reorganize into 説明書/予定/archive; update docs/README.md and CLAUDE.md; move root .nyash to local_tests; consolidate native-plan notes into README + archive

local_tests/test_array_simple.nyash

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+// ArrayBox簡単なテスト
+print("=== ArrayBox簡単なテスト ===")
+
+local arr
+arr = new ArrayBox()
+print("Created ArrayBox")
+
+// 要素を追加
+arr.push("Hello")
+arr.push("World")
+print("Added elements")
+
+// 長さを確認
+print("Length: " + arr.length())
+
+// 配列の内容を表示
+print("Array: " + arr.toString())
+
+// 要素を取得
+print("First element: " + arr.get(0))
+print("Second element: " + arr.get(1))
+
+print("\n=== Test complete! ===")