Public contract surface for the calendarius extension (ext-<id> convention): shared happening vocabulary + HappeningsFacade interface. Depends only on stdlib - never another extension.
Public contract surface for the contactus extension (per the extension-contract-repo convention): backend Go module + frontend @sneat/extension-contactus-contract lib. Depends only on foundational/core — never another extension.
Public contract surface for the gameboard extension (extension-contract-repo convention): TypeSpec api4gameboard + Go backend contract module + @sneat/extension-gameboard-contract. Depends only on foundational/core — never another extension.