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

[Yeom-JinHo]

Description

This PR updates the isSafeInteger utility to behave as a proper TypeScript type predicate.
Previously, it only returned a boolean value, which did not narrow the input type.
Now it returns value is number, aligning with the JSDoc description and enabling type narrowing in conditional branches.

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Changes

• Type Predicate Update (major fix):
  Updated the return type from boolean → value is number.
  This allows TypeScript to narrow the argument type to number when the function returns true.

• Parameter Type Refinement:
  Changed the parameter type from any → unknown for safer type inference.

• Documentation Update:
  Modified MDX docs:

  • Updated Parameters and Returns table to reflect the new type predicate.
  • Added a TypeScript note section explaining type narrowing behavior.

• Type Test Update:
  Added a dedicated type predicate test case verifying that the value is narrowed to number inside conditional blocks.

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Motivation

The previous implementation’s JSDoc claimed that it could “serve as a type predicate,”
but in reality, it didn’t provide any type narrowing because the function signature returned a plain boolean.
This update ensures that the function now truly behaves as a type guard, matching both runtime behavior and TypeScript semantics.

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Breaking Changes

• No runtime behavior changes.
• Type-level change:
  Projects relying on an explicit boolean return type may need to update dependent type definitions or mocks.

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Project	Deployment	Preview	Comments	Updated (UTC)
es-toolkit	Ready	Preview	Comment	Nov 13, 2025 9:01am

[Copilot]

Pull Request Overview

This PR enhances the isSafeInteger function to use TypeScript's type predicate feature, enabling better type narrowing. The function signature is updated from returning boolean to returning value is number, and the parameter type is improved from any to unknown.

Key Changes

• Updated function signature to use TypeScript type predicate (value is number)
• Changed parameter type from any to unknown for better type safety
• Updated JSDoc comments and documentation across all language versions to reflect the type predicate behavior

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/compat/predicate/isSafeInteger.ts	Updated function signature to use type predicate and improved parameter type from any to unknown
docs/reference/compat/predicate/isSafeInteger.md	Added documentation explaining the type predicate behavior in English
docs/zh_hans/reference/compat/predicate/isSafeInteger.md	Added documentation explaining the type predicate behavior in Chinese
docs/ko/reference/compat/predicate/isSafeInteger.md	Added documentation explaining the type predicate behavior in Korean
docs/ja/reference/compat/predicate/isSafeInteger.md	Added documentation explaining the type predicate behavior in Japanese

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[raon0211]

Thanks!