fix: stdlib success return types

[haithium]

No description provided.

[gemini-code-assist]

Summary of Changes

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This pull request focuses on improving the consistency and clarity of return types in the standard library, specifically within the io and os modules. By changing the success return type to true? and adding an optional error code for os.remove and os.rename, the PR aims to provide more precise and informative feedback to users of these functions.

Highlights

• Return Type Consistency: This PR standardizes the return types for success in io and os library functions to true?.
• Enhanced Error Information: The os.remove and os.rename functions now include an optional errcode return value for more detailed error reporting.

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[gemini-code-assist]

Code Review

This pull request refines the return type annotations for several standard library functions in io.lua and os.lua. The changes correctly replace the generic boolean or boolean? with the more specific true? for success return values, which accurately reflects that these functions return true on success and nil on failure. Additionally, for os.remove and os.rename, the annotations are improved by correcting the nullability of the success return value and adding the missing errcode integer that is returned on failure. These changes improve the accuracy and precision of the type definitions, which is beneficial for static analysis.