What problems was I solving

A set of 16 scaffolding symbols added to api-builder's schema registry in #1048 was never adopted by any caller, yet remained in the source and in the public barrel export. This dead code created ongoing maintenance noise, inflated the public API surface, and risked future developers building on abandoned abstractions.

What user-facing changes did I ship

No user-facing behavior changes. Downstream packages will see a smaller public export surface from @architect/api-builder, but the removed symbols had no known consumers.

How I implemented it

Deleted the unused interfaces, classes, constants, and free functions from schema-registry.ts, then removed three corresponding dead re-exports from api-builder/main/index.ts. Removal was validated with git log -S across the full repository history and with codebase-wide usage searches, confirming every removed symbol has zero consumers.

Description for the changelog

Removes 16 unused schema-registry scaffolding symbols and three dead barrel exports from api-builder. The kept SchemaRegistry class, getGlobalRegistry, and registerSchema remain available for active OpenAPI generation paths. This is a non-breaking cleanup because no downstream code imported the removed symbols.