Unified Stream trait: read() and write() on one type

Stream trait: read() returns PesFrame, write() accepts PesFrame.
A stream is a stream — you read from it or write to it.
No separate Input/Output traits.

API: libfreemkv::input(url) and libfreemkv::output(url, title, codecs)
Returns Box<dyn Stream>.

src/drive/macos.rs

@@ -7,7 +7,9 @@ pub fn find_drives() -> Vec<(String, DriveId)> {
     let mut drives = Vec::new();
     for i in 0..16 {
         let path = format!("/dev/disk{}", i);
-        if !std::path::Path::new(&path).exists() { continue; }
+        if !std::path::Path::new(&path).exists() {
+            continue;
+        }
         match crate::scsi::open(std::path::Path::new(&path)) {
             Ok(mut transport) => {
                 if let Ok(id) = DriveId::from_drive(transport.as_mut()) {