[Task] Document the split-client migration and contribution workflow

[Aias00]

Description

Background

Community contributors need a clear guide for contributing to the split Java client repository and for making coordinated changes across the main ShenYu repo and shenyu-client-java.

Tasks

• Explain why the Java client is split from the main repo.
• Explain the different JDK policies for client repo and main repo.
• Explain how to build and test shenyu-client-java.
• Explain how to run JDK 8/17/21/23/25 verification.
• Explain how to test local client artifacts with main repo admin/bootstrap.
• Explain when a change requires PRs in both repositories.
• Add a PR checklist for client repo changes.
• Add a PR checklist for main repo changes that affect client compatibility.

Expected Output

Contributor-facing documentation.

Acceptance Criteria

• A new contributor can understand where to make client-related changes.
• The documentation includes local verification commands.
• The documentation explains cross-repo compatibility expectations.

Task List

No response

[github-actions]

👋 Hello @Aias00

A new issue has been opened by @Aias00:

• Title: [Task] Document the split-client migration and contribution workflow
• Link: [Task] Document the split-client migration and contribution workflow #6373

Please review when you have time. Thank you! 🙏