fix: revert content type change in #850

Author: danielgtaylor

huma.go

@@ -499,6 +499,8 @@ func writeResponse(api API, ctx Context, status int, ct string, body any) error
 		if ctf, ok := body.(ContentTypeFilter); ok {
 			ct = ctf.ContentType(ct)
 		}
+
+		ctx.SetHeader("Content-Type", ct)
 	}
 
 	if err := transformAndWrite(api, ctx, status, ct, body); err != nil {
@@ -543,8 +545,6 @@ func transformAndWrite(api API, ctx Context, status int, ct string, body any) er
 		}
 	}
 
-	ctx.SetHeader("Content-Type", ct)
-
 	return nil
 }