Fix go mod tidy checks

[akalipetis]

• feat(lint): go mod tidy
• feat(dev): lint go mod or error in linting
• feat(ci): bump setup-go and use go.mod for Go version

[Copilot]

Pull Request Overview

This PR improves the Go module linting process by replacing a complex shell-based mod tidy check with Go's built-in -diff flag and updates the CI workflow to use the latest setup-go action with automatic Go version detection.

• Simplifies go mod tidy validation using the native -diff flag instead of shell scripting
• Updates GitHub Actions to use setup-go@v6 and reads Go version from go.mod file
• Removes complex shell logic that parsed go mod tidy output for unused dependencies

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
Makefile	Replaces complex shell-based go mod tidy check with simpler -diff flag
.github/workflows/ci.yml	Updates setup-go action version and switches to go.mod for version detection

---

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