refactor: replace any with safer type for package.json rewrite

[gwagjiug]

Summary

Replaced the use of any in the rewrite function of loadConfig with a safer type definition:
PackageJson & Record<string, unknown>.

Details

• Previously, pkg was typed as any, which bypassed TypeScript's type checking and could lead to unsafe property access.
• Updated to PackageJson & Record<string, unknown>:
  • PackageJson provides type safety for standard package.json fields.
  • Record<string, unknown> allows custom fields to be safely accessed.
• As a result, we maintain both flexibility (supporting custom config fields) and type safety.

Why

This change removes unsafe any usage while keeping compatibility with user-defined fields in package.json, ensuring more reliable type checks and better developer experience.

[vercel]

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