Refactor create_file for posix

[bugdea1er]

Remove the create_file(std::error_code&) overload

[Copilot]

Pull Request Overview

This PR refactors the create_file function for POSIX environments by removing the error-code–returning overload and inlining temporary-file creation logic in the default overload. Key changes include:

• Removal of the create_file(std::error_code&) overload.
• Inlining the logic to first try O_TMPFILE and fallback to mkstemp, storing errno before unlinking.
• Throwing a fs::filesystem_error on failure instead of returning an error code.

Comments suppressed due to low confidence (1)

src/create.cpp:202

• [nitpick] Consider renaming 'create_error' to something like 'mkstemp_errno' to better convey that it captures the errno value post mkstemp.

int create_error = errno;

[Copilot]

Pull Request Overview

This PR refactors the temporary file creation logic on POSIX systems by removing the error_code–based overload and introducing exception–based error handling.

• Removed the legacy create_file(std::error_code&) overload
• Updated the create_file() function to use exception throwing on file creation failure
• Simplified and centralized the temporary file creation flow using O_TMPFILE and mkstemp

Comments suppressed due to low confidence (2)

src/create.cpp:154

• [nitpick] The removal of the error_code-based overload changes the error handling behavior. Please verify that all call sites have been updated to handle exceptions instead of error codes.

#else

src/create.cpp:202

• [nitpick] Since this branch now throws an exception on mkstemp failure, make sure that the exception handling is consistent with the rest of the project and that callers are prepared for this behavior shift.

if (handle == -1) {