A test server returns a valid 200 OK JSON body ({"name":"alice"}). The chaos
rule rewrites the successful response body to malformed JSON before the
client sees it, exercising the caller's decode-failure fallback: FetchName
returns "unknown" instead of panicking or returning a bogus value.
go run . # prints: unknown
go test ./... # asserts the degraded path and the clean (no-chaos) path
Command response-mutate demonstrates fault.ResponseMutate via
adapter/http.MutateResponse: chaos corrupts the body of an otherwise
successful 200 response, and the client's decode path degrades gracefully
(returns "unknown") instead of crashing.