fix(peer): forward UploadFailed to the download store

The code 46 handler parsed the filename and only logged it, so a queued
download whose peer reported an upload failure never received
DownloadStatus::Failed and hung until the caller's own timeout.

The handler now sends PeerMessage::UploadFailed through the dispatcher
and the actor stamps the peer's username on it before forwarding
ClientOperation::UploadFailed into the existing failure path. The
variant's username field stays for API compatibility; the wire message
cannot name anyone but the connected peer, so the actor supplies it.

Fixes #30

soulseek-rs-lib/src/message/peer/upload_failed.rs

@@ -10,8 +10,31 @@ impl MessageHandler<PeerMessage> for UploadFailedHandler {
     fn get_code(&self) -> u8 {
         46
     }
-    fn handle(&self, message: &mut Message, _sender: Sender<PeerMessage>) {
+    fn handle(&self, message: &mut Message, sender: Sender<PeerMessage>) {
         let filename = message.read_string();
         info!("Upload failed for {}", filename);
+        let _ = sender.send(PeerMessage::UploadFailed(String::new(), filename));
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::message::framed;
+
+    #[test]
+    fn the_failed_filename_is_forwarded() {
+        let (tx, rx) = std::sync::mpsc::channel();
+        let mut message = framed(|m| {
+            m.write_string("@@share\\gone.mp3");
+        });
+
+        UploadFailedHandler.handle(&mut message, tx);
+        match rx.try_recv() {
+            Ok(PeerMessage::UploadFailed(_, filename)) => {
+                assert_eq!(filename, "@@share\\gone.mp3");
+            }
+            other => panic!("unexpected: {other:?}"),
+        }
     }
 }