Refactor publish workflow to use explicit project paths

[KrastyTC]

Replaces auto-detection of library and test projects with explicit environment variables for project paths. Simplifies restore, build, test, and pack steps to use these variables directly, improving reliability and maintainability of the workflow.

[Copilot]

Pull Request Overview

This PR refactors the GitHub Actions publish workflow to replace automatic project detection with explicit environment variables for project paths. This change improves workflow reliability by removing complex detection logic and making project paths configurable.

Key changes:

• Replaces project auto-detection with explicit environment variables LIB_PROJ and TEST_PROJ
• Simplifies restore, build, test, and pack steps to use these predefined paths
• Adds better error handling and output formatting

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}