Fix syntax error in print_demo.html caused by CRLF and backslash string continuation

app/src/main/assets/print_demo.html

@@ -525,18 +525,19 @@
     // ES6 特性测试函数（通过 eval 避免阻塞旧版 JS 引擎整体解析）
     function testES6Features() {
         try {
-            eval("\
-                const arr = [1, 2, 3];\
-                const [a, ...rest] = arr;\
-                let sum = rest.reduce((acc, val) => acc + val, 0);\
-                const myMap = new Map();\
-                myMap.set('key', `Sum is ${sum}`);\
-                new Promise((resolve) => {\
-                    setTimeout(() => resolve(myMap.get('key')), 100);\
-                }).then(res => {\
-                    alert(`ES6 引擎测试成功!\\n解构: a=${a}\\nPromise/Map 返回: ${res}`);\
-                });\
-            ");
+            var code = [
+                "const arr = [1, 2, 3];",
+                "const [a, ...rest] = arr;",
+                "let sum = rest.reduce((acc, val) => acc + val, 0);",
+                "const myMap = new Map();",
+                "myMap.set('key', `Sum is ${sum}`);",
+                "new Promise((resolve) => {",
+                "    setTimeout(() => resolve(myMap.get('key')), 100);",
+                "}).then(res => {",
+                "    alert(`ES6 引擎测试成功!\\n解构: a=${a}\\nPromise/Map 返回: ${res}`);",
+                "});"
+            ].join("");
+            eval(code);
         } catch(e) {
             alert("ES6 测试失败 (当前环境可能不支持): " + e.message);
         }