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/transfer.rs

@@ -504,7 +504,7 @@ mod tests {
         CatalogContentManifestBody,
         CatalogExtractedEntry,
     };
-    use tokio::sync::{RwLock, mpsc};
+    use tokio::sync::RwLock;
     use tokio_util::task::TaskTracker;
 
     use super::*;
@@ -611,7 +611,7 @@ mod tests {
         root: &Path,
         manifest: &CatalogContentManifest,
         provider: Arc<CountingStreamInstallProvider>,
-    ) -> (PeerCtx, mpsc::UnboundedReceiver<crate::PeerEvent>) {
+    ) -> (PeerCtx, crate::PeerEventReceiver) {
         let catalog = Arc::new(
             CatalogBundle::from_manifests([manifest.clone()])
                 .expect("test catalog should be complete"),
@@ -643,7 +643,7 @@ mod tests {
                 availability: Availability::Ready,
             },
         );
-        let (tx, rx) = mpsc::unbounded_channel();
+        let (tx, rx) = crate::peer_event_channel();
         (ctx.to_peer_ctx(tx, CancellationToken::new()), rx)
     }