data: A3 提效对比实验数据（23 样例 + 人工基线 + 插件实测，整体提速约 266 倍）

- data/efficiency-samples/ 23 个多语言样例 + data/manual-review-tool.html 人工审核工具
- tests/measure/measure-plugin-samples.mjs 四语言插件侧测量脚本
- tests/measure/compare-a3.mjs 聚合对比 + results（插件实测/人工基线/comparison）
- performance-comparison.md 填实基线对比与结论；README 效果总结由占位改为真实数据

data/efficiency-samples/java/PaymentService.java

@@ -0,0 +1,28 @@
+public class PaymentService {
+
+    private static final String DEFAULT_USER = "guest";
+
+    public void register(String userName) {
+        String password = "admin123";
+        System.out.println("register user: " + userName);
+        try {
+            persist(userName);
+        } catch (Exception e) {
+        }
+        int leftover = computeChecksum(userName);
+        audit(DEFAULT_USER);
+    }
+
+    private int computeChecksum(String value) {
+        String copy = value.toString();
+        return copy.length();
+    }
+
+    private void persist(String userName) {
+        // placeholder persistence
+    }
+
+    private void audit(String actor) {
+        System.out.println("audit by " + actor);
+    }
+}