docs: Add missing api-spec/BREAKING_CHANGES.md referenced in README

[Dunsin-cyber]

While onboarding and exploring the codebase to understand the protocol implementation, I noticed that the README.md references a document intended to guide contributors on breaking changes and Protobuf best practices:

api-spec/BREAKING_CHANGES.md

However, this file does not currently exist in the repository.

Working on This? Yes

[arkanaai]

Triage

Classification: docs — missing file referenced in README.

The README at line 345 links to api-spec/BREAKING_CHANGES.md which does not exist. The api-spec/ directory currently contains only:

• openapi/
• protobuf/

Suggested approach: Create api-spec/BREAKING_CHANGES.md covering Protobuf best practices for this repo (field numbering, deprecation policy, backward-compat rules for gRPC APIs). The existing openapi/ and protobuf/ directories can serve as context for what breaking changes are most relevant.

[arkanaai]

Welcome to the Ark project, @Dunsin-cyber! 👋 Thanks for opening this issue.
If you need help or context, feel free to ask — we're happy to help.