feat: 新增内置函数input

examples/input.ast

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+let name = input("Your name: ");
+print("Hello, " + name)

examples/script.ast

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+// 压测：循环、递归、闭包
+
+fn fib(n) {
+    if (n <= 1) {
+        return n
+    }
+    return fib(n - 1) + fib(n - 2)
+}
+
+fn make_adder(x) {
+    return fn(y) { return x + y }
+}
+
+let t0 = clock()
+
+// 1. 循环压测：100万次算术
+let sum = 0
+let i = 0
+while (i < 1000000) {
+    sum = sum + i
+    i = i + 1
+}
+print("loop 1M:", sum)
+
+// 2. 递归压测：fib(25)
+let f = fib(25)
+print("fib(25):", f)
+
+// 3. 闭包压测：100万次调用
+let add10 = make_adder(10)
+let j = 0
+let total = 0
+while (j < 1000000) {
+    total = add10(j)
+    j = j + 1
+}
+print("closure 1M calls:", total)
+
+let t1 = clock()
+print("total time (s):", t1 - t0)