Fix mac native packaging in CI

[KSemenenko]

Summary

• ensure the CI pack steps pass the macOS native binary explicitly and log what is being packed
• harden the package validation to inspect every produced nupkg and fail if none contain the native library
• resolve the mac native binary paths from the project directory so local and CI builds locate the artifact reliably

Testing

• not run (dotnet CLI not available in container)

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https://chatgpt.com/codex/tasks/task_e_68e229d761248326b7098a2b8b83fdc3

[Copilot]

Pull Request Overview

This PR fixes macOS native packaging in CI by improving path resolution and validation logic. The changes ensure that the macOS native binary is properly located and included in packages during CI builds.

• Improved path resolution using MSBuild functions to locate native binaries reliably across different environments
• Enhanced CI logging to show which native binary is being packed
• Hardened package validation to inspect all produced packages and fail if any lack the native library

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/MLXSharp/MLXSharp.csproj	Updated path resolution to use MSBuild functions for reliable cross-platform path handling
.github/workflows/ci.yml	Enhanced CI pack steps with explicit logging and improved package validation logic

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