fix(peer): coalesce full UI view publications

Keep one queued and one replaceable pending snapshot for remote-library and Call-to-Play views while preserving lifecycle-event FIFO delivery. Generation barriers and fenced drains prevent stale nonempty views from crossing disable or acknowledgement boundaries.

Test Plan:
- just test
- just clippy
- focused burst, lifecycle ordering, fence, repeated-barrier, and stale-view tests
- independent ordering review
- git diff --check

crates/lanspread-peer/src/services/discovery.rs

@@ -12,13 +12,14 @@ use futures::{StreamExt as _, stream::FuturesUnordered};
 use lanspread_mdns::{LANSPREAD_SERVICE_TYPE, MdnsBrowser, MdnsService, MdnsServicePoll};
 use lanspread_proto::{PROTOCOL_VERSION, PeerEndpoint, PeerId};
 use tokio::sync::{
-    mpsc::{self, UnboundedSender},
+    mpsc,
     oneshot,
 };
 use tokio_util::sync::CancellationToken;
 
 use crate::{
     PeerEvent,
+    PeerEventSender,
     context::NetworkServiceCtx,
     events,
     services::{
@@ -188,7 +189,7 @@ impl Drop for DiscoveryWorker {
 /// Runs the peer discovery service using mDNS.
 #[allow(clippy::too_many_lines)]
 pub async fn run_peer_discovery(
-    tx_notify_ui: UnboundedSender<PeerEvent>,
+    tx_notify_ui: PeerEventSender,
     ctx: NetworkServiceCtx,
 ) -> eyre::Result<()> {
     log::info!("Starting peer discovery task");