feat: Windows GUI development with egui - simple notepad example

- Fixed EguiBox Send+Sync trait bounds for thread safety
- Added missing Arc import for EguiBox implementation
- Simplified font setup in Windows notepad example
- Successfully built 4.5MB Windows GUI executable
- Nyash can now create native Windows desktop applications! 🎉

local_tests/test_windows_basic.nyash

@@ -0,0 +1,13 @@
+// 最もシンプルなWindowsテスト
+print("Hello Windows!")
+print("1 + 1 = " + (1 + 1))
+print("Nyash is running!")
+
+// ループテスト
+local i = 0
+loop(i < 3) {
+    print("Count: " + i)
+    i = i + 1
+}
+
+print("Done!")

local_tests/test_windows_hello.nyash

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+// Windows実行テスト
+local console = new ConsoleBox()
+console.log("🎉 Hello from Windows Nyash!")
+console.log("Everything is Box on Windows too! 🐱")
+
+// 基本的な計算テスト
+local math = new MathBox()
+local result = math.add(10, 32)
+console.log("10 + 32 = " + result)
+
+// StringBoxテスト
+local str = new StringBox("Windows")
+console.log("Running on: " + str.value)
+
+print("✨ Nyash works perfectly on Windows! ✨")

local_tests/test_windows_simple.nyash

@@ -0,0 +1,26 @@
+// シンプルなWindowsテスト
+print("🎉 Nyash on Windows!")
+print("Everything is Box!")
+
+// 基本的な文字列操作
+local str1 = new StringBox("Hello")
+local str2 = new StringBox("Windows")
+print(str1.value + " " + str2.value + "!")
+
+// 数値演算（直接）
+local num1 = new IntegerBox(42)
+local num2 = new IntegerBox(8)
+print("Answer: " + num1.value + " + " + num2.value + " = " + (num1.value + num2.value))
+
+// ArrayBoxテスト
+local arr = new ArrayBox()
+arr.push("First")
+arr.push("Second")
+arr.push("Third")
+print("Array length: " + arr.length())
+
+// MapBoxテスト
+local map = new MapBox()
+map.set("os", "Windows")
+map.set("arch", "x86_64")
+print("Running on: " + map.get("os"))