fix(isSafeInteger): implement type predicate to narrow type to number

docs/ja/reference/compat/predicate/isSafeInteger.md

@@ -56,4 +56,9 @@ isSafeInteger(NaN); // false
 
 #### 戻り値
 
-(`boolean`): 値が安全な整数の場合は `true`、そうでなければ `false` を返します。
+(`value is number`): 値が安全な整数の場合は `true`、そうでなければ `false` を返します。  
+`true` を返す場合、TypeScript は `value` の型を `number` に絞り込みます。
+
+> 🧠 **TypeScript 注記:**  
+> この関数は **型 predicate** として機能します。つまり、`true` を返す場合、  
+> TypeScript は引数の型を `number` に絞り込みます。

docs/ko/reference/compat/predicate/isSafeInteger.md

@@ -56,4 +56,9 @@ isSafeInteger(NaN); // false
 
 #### 반환 값
 
-(`boolean`): 값이 안전한 정수이면 `true`, 아니면 `false`를 반환해요.
+(`value is number`): 값이 안전한 정수이면 `true`, 아니면 `false`를 반환해요.  
+`true`를 반환할 때, TypeScript는 `value`의 타입을 `number`로 좁혀요.
+
+> 🧠 **TypeScript 참고:**  
+> 이 함수는 **타입 predicate**로 동작해요. 즉, `true`를 반환할 때  
+> TypeScript는 인자 타입을 `number`로 좁혀요.

docs/reference/compat/predicate/isSafeInteger.md

@@ -56,4 +56,9 @@ isSafeInteger(NaN); // false
 
 #### Returns
 
-(`boolean`): Returns `true` if the value is a safe integer, otherwise `false`.
+(`value is number`) Returns `true` if the value is a safe integer, otherwise `false`.  
+When `true`, TypeScript narrows the type of `value` to `number`.
+
+> 🧠 **TypeScript note:**  
+> This function acts as a **type predicate**, meaning that when it returns `true`,  
+> TypeScript will narrow the argument type to `number`.

docs/zh_hans/reference/compat/predicate/isSafeInteger.md

@@ -54,4 +54,9 @@ isSafeInteger(NaN); // false
 
 #### 返回值
 
-(`boolean`): 如果值为安全整数则返回 `true`，否则返回 `false`。
+(`value is number`): 如果值为安全整数则返回 `true`，否则返回 `false`。  
+当返回 `true` 时，TypeScript 会将 `value` 的类型缩小为 `number`。
+
+> 🧠 **TypeScript 说明：**  
+> 此函数作为 **类型谓词** 使用，这意味着当它返回 `true` 时，  
+> TypeScript 会将参数类型缩小为 `number`。

src/compat/predicate/isSafeInteger.ts

@@ -4,17 +4,18 @@
  * A safe integer is an integer that can be precisely represented as a `number` in JavaScript,
  * without any other integer being rounded to it.
  *
- * This function can also serve as a type predicate in TypeScript, narrowing the type of the argument to `number`.
+ * This function also serves as a type predicate in TypeScript,
+ * narrowing the type of the argument to `number`.
  *
  * @param {unknown} value - The value to check
- * @returns {boolean} `true` if `value` is an integer and between the safe values, otherwise `false`
+ * @returns {value is number} `true` if `value` is an integer and between the safe values, otherwise `false`
  *
  * @example
  * isSafeInteger(3); // Returns: true
  * isSafeInteger(Number.MIN_SAFE_INTEGER - 1); // Returns: false
  * isSafeInteger(1n); // Returns: false
  * isSafeInteger('1'); // Returns: false
  */
-export function isSafeInteger(value: any): boolean {
+export function isSafeInteger(value: unknown): value is number {
   return Number.isSafeInteger(value);
 }