[DevMPoveaCL]

Summary

• Aggregates the reviewed API/interface design chain into the main playbook flow.
• Adds a canonical API topic covering REST, SOAP, gRPC, WebSocket, Webhooks, GraphQL, and WebRTC.
• Clarifies boundaries in related topics and integrates navigation between Networking and SQL.

Chain Context

main
└─ 📍 final tracker: feat/expand-api-design-content
   ├─ PR #9: API topic content
   ├─ PR #10: boundary cleanup
   └─ PR #11: navigation + lint verification

Changes

Area	Change
API_AND_INTERFACE_DESIGN/	New 3-level canonical topic for API/interface design.
Related docs	Networking, System Design, React+SpringBoot, and JS now point API design decisions to the canonical topic.
Navigation	Root README, Networking, and SQL place API topic between Networking and SQL.
.markdownlint.json	Captures didactic Markdown lint conventions used by this repo.

Testing

• npx --yes markdownlint-cli API_AND_INTERFACE_DESIGN/**/*.md
• Changed-file markdownlint check passed during SDD verify.
• git diff --check HEAD~1..HEAD
• SDD verify final verdict: PASS WITH WARNINGS.

Known Warnings

• Repo-wide markdownlint has unrelated baseline failures.
• lychee did not resolve via npx during verification.

Acceptance Checklist

• Chained PRs reviewed/merged in order: docs: add API interface design topic #9 → docs: clarify API design boundaries #10 → docs: integrate API topic navigation #11.
• Scope is documentation/tooling config only.
• Out-of-scope quality baseline issues are documented.
• No .atl/ local agent artifacts included.
• Conventional commit format used.

Closes #8