[jm-rivera]

The proxy's own problem documents, added in #64, link type to /codes/rate_limited and /codes/transient_unavailable, and src/app/codes/[code]/route.ts forwarded both to the API, whose registry holds only API codes, so each link answered 404 code_not_found. Both SDK clients expose that link as docsUrl.

The route now answers a proxy-owned code locally before it forwards anything else. src/lib/proxy/proxyCodes.ts builds the entry in the API's CodeRegistryEntry shape (code, classification: refusal, definition, lifecycle: active, mappings: [], title, detail: null) from src/lib/proxy/proxy-codes.json, a copy of the client contract's proxy-codes.json at spec-kit 0d19172, which the vendored client does not ship with its condition text. Each title matches the problem document the site sends for the same code. docs/development.md says to re-copy the file when the contract changes.

src/lib/proxy/test/proxyCodes.test.ts checks every code in REGISTRY_CODES: a proxy code gets a local entry, any other code is left to the forward, every proxy code in the contract is in REGISTRY_CODES, and the entry's shape and title match. The route handler itself imports server-only and has no unit harness; it calls proxyCodeEntry before codeTarget.

Testing: pnpm typecheck, pnpm lint, prettier on changed files and pnpm build passed; the proxy unit tests passed (119). db/test was not run, since nothing it covers changed.