fix: unified raw room names + merged presence on join

1. CLI client now sends raw room names (no hash), matching Android
   JNI and Desktop Tauri. All three clients are now consistent.

2. When a client joins a global room, the relay merges federated
   remote participants into the initial RoomUpdate. Previously,
   clients that joined after the GlobalRoomActive signal only saw
   local participants. Now they see everyone immediately.

3. Added get_remote_participants() to FederationManager for querying
   cached remote participants from all peer links.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/wzp-relay/src/main.rs

@@ -15,7 +15,7 @@ use std::time::Duration;
 use tokio::sync::Mutex;
 use tracing::{error, info, warn};
 
-use wzp_proto::MediaTransport;
+use wzp_proto::{MediaTransport, SignalMessage};
 use wzp_relay::config::RelayConfig;
 use wzp_relay::metrics::RelayMetrics;
 use wzp_relay::pipeline::{PipelineConfig, RelayPipeline};
@@ -741,7 +741,29 @@ async fn main() -> anyhow::Result<()> {
                         Ok((id, update, senders)) => {
                             metrics.active_rooms.set(mgr.list().len() as i64);
                             drop(mgr); // release lock before async broadcast
-                            room::broadcast_signal(&senders, &update).await;
+
+                            // Merge federated participants into RoomUpdate if this is a global room
+                            let merged_update = if let Some(ref fm) = federation_mgr {
+                                if fm.is_global_room(&room_name) {
+                                    if let SignalMessage::RoomUpdate { count: _, participants: mut local_parts } = update {
+                                        let remote = fm.get_remote_participants(&room_name).await;
+                                        if !remote.is_empty() {
+                                            local_parts.extend(remote);
+                                            SignalMessage::RoomUpdate {
+                                                count: local_parts.len() as u32,
+                                                participants: local_parts,
+                                            }
+                                        } else {
+                                            SignalMessage::RoomUpdate {
+                                                count: local_parts.len() as u32,
+                                                participants: local_parts,
+                                            }
+                                        }
+                                    } else { update }
+                                } else { update }
+                            } else { update };
+
+                            room::broadcast_signal(&senders, &merged_update).await;
                             id
                         }
                         Err(e) => {