fix(client): survive the review findings on the thread-flood fix

Review of the capacity work surfaced three real defects and two gaps:

- A peer dribbling bytes re-armed the 10s handshake read timeout on
  every read and held its accept permit forever; 128 such sockets
  wedged the accept loop for good. The handshake now has one deadline
  across all reads, plus a 4 KiB cap on buffered handshake bytes.
- A capacity refusal was logged and swallowed, leaving the refused
  peer's queued downloads stuck until the caller's own timeout. Both
  registration paths now fail those downloads so the caller gets a
  verdict, and the listener only announces PeerConnected when the
  registration actually happened.
- The transfer-claim was undone by the worker thread writing Queued
  back over it; that write is gone, so a replayed TransferResponse
  can no longer start a second writer on the same .part file.
- Offered uploads and queue waiters joined the eviction-protected
  set, and the browse protection window matches the minutes a real
  share listing takes rather than one.

Regression tests: the broker-timeout sweep failing a queued download
end to end, the replay guard observed over a real socket, and the
handshake deadline against a dribbling and an oversized peer.

soulseek-rs-lib/src/client/mod.rs

@@ -60,7 +60,7 @@ const BROKER_CONNECT_TIMEOUT: Duration = Duration::from_secs(20);
 
 const DEFAULT_MAX_PEERS: usize = 512;
 
-const BROWSE_PROTECT_WINDOW: Duration = Duration::from_mins(1);
+const BROWSE_PROTECT_WINDOW: Duration = Duration::from_mins(5);
 
 /// Source of non-zero correlation tokens for server-brokered connections.
 static NEXT_CONNECT_TOKEN: AtomicU32 = AtomicU32::new(1);
@@ -634,6 +634,9 @@ impl ClientContext {
             .collect();
         protected
             .extend(self.active_uploads.values().map(|u| u.username.clone()));
+        protected.extend(self.uploads.values().map(|j| j.downloader.clone()));
+        protected
+            .extend(self.upload_queue.iter().map(|q| q.downloader.clone()));
         protected.extend(self.pending_serves.keys().cloned());
         protected.extend(self.pending_peer_messages.keys().cloned());
         let now = Instant::now();