fix(docs): correct CONTRIBUTING.md relative link in agentmesh-avp README

[Ricky-G]

Description

Fixes the failing Markdown Link Check workflow (job 72488648923) by correcting a broken relative link in the agentmesh-avp README.

The README at packages/agentmesh-integrations/agentmesh-avp/README.md is nested 3 directories deep, so the relative link to the repo-root CONTRIBUTING.md needs ../../../, not ../../. The previous path resolved to packages/CONTRIBUTING.md (which does not exist), causing lychee to fail with:

[ERROR] file:///.../packages/CONTRIBUTING.md | Cannot find file: File not found. Check if file exists and path is correct

Change

- See the main [CONTRIBUTING.md](../../CONTRIBUTING.md) for guidelines.
+ See the main [CONTRIBUTING.md](../../../CONTRIBUTING.md) for guidelines.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Maintenance (dependency updates, CI/CD, refactoring)
• Security fix

Package(s) Affected

• agent-os-kernel
• agent-mesh
• agent-runtime
• agent-sre
• agent-governance
• docs / root

(Specifically: packages/agentmesh-integrations/agentmesh-avp/README.md)

Checklist

• My code follows the project style guidelines (ruff check) — N/A, docs-only change
• I have added tests that prove my fix/feature works — verified by re-running the lychee link checker against the updated README
• All new and existing tests pass (pytest) — N/A, no code changes
• I have updated documentation as needed
• I have signed the Microsoft CLA

Attribution & Prior Art

• This contribution does not contain code copied or derived from other projects without attribution
• Any external projects that inspired this design are credited in code comments or documentation
• If this PR implements functionality similar to an existing open-source project, I have listed it below

Prior art / related projects (if any):
N/A — single-character relative path correction.