Docs: API behavior needs reader-facing documentation

[moxie-docs]

This documentation PR captures the current guidance for documenting API behavior and how backend/frontend contracts should be reflected and extended, emphasizing alignment with existing patterns and the need to load conventions from the Moxie Docs MCP server before edits.

What these docs cover

• AGENTS.md provides explicit expectations for when and how to update docs and how to ensure consistency across edits
• Documentation guidance stresses loading conventions and patterns from the Moxie Docs MCP server prior to edits
• Entry points and contracts are inferred from repository files and emphasize that there is no explicit HTTP route or API contract described yet
• Backend/README.md is currently empty and does not document inputs, outputs, or error cases
• If new API routes are introduced, the guidance suggests adding per-route sections with HTTP methods, paths, inputs, outputs, and error cases

How to review

• Verify AGENTS.md rules are present and clearly state when to update docs and how to maintain consistency
• Check that the doc notes loading conventions/patterns from the Moxie Docs MCP server before edits
• Confirm there is no explicit per-route API contract documented in the provided files
• Ensure the entry points/contract inference section correctly states there are no defined HTTP routes or API contracts in the current source
• Verify guidance sections mention that backend/README.md is empty and contains no inputs/outputs or error cases

Documentation updated

• moxie-docs/get-started/backend-readme.md

Referenced sources

• backend/README.md
• AGENTS.md