fix: fill subscriber address before calling .peer() to avoid panic

PR #2172 added detailed tracing that calls subscriber.peer() BEFORE
filling in the address from source_addr. This causes a panic when the
subscriber has PeerAddr::Unknown (NAT peers).

The correct order (from PR #2171) is:
1. Check if address is unknown
2. Fill in address from source_addr
3. THEN call .peer() for tracing

This regression was introduced when merging PR #2172's tracing
improvements without preserving the correct order of operations.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: sanity

crates/core/src/operations/subscribe.rs

@@ -410,25 +410,28 @@ impl Operation for SubscribeOp {
                     // Fill in subscriber's external address from transport layer if unknown.
                     // This is the key step where the first recipient (gateway) determines the
                     // subscriber's external address from the actual packet source address.
+                    // IMPORTANT: Must fill address BEFORE any .peer() calls to avoid panic.
                     let mut subscriber = subscriber.clone();
 
+                    if subscriber.peer_addr.is_unknown() {
+                        if let Some(addr) = source_addr {
+                            subscriber.set_addr(addr);
+                            tracing::debug!(
+                                tx = %id,
+                                %key,
+                                subscriber_addr = %addr,
+                                "subscribe: filled subscriber address from source_addr"
+                            );
+                        }
+                    }
+
                     tracing::debug!(
                         tx = %id,
                         %key,
-                        subscriber_orig = %subscriber.peer(),
+                        subscriber = %subscriber.peer(),
                         source_addr = ?source_addr,
                         "subscribe: processing RequestSub"
                     );
-
-                    if let Some(addr) = source_addr {
-                        subscriber.set_addr(addr);
-                        tracing::debug!(
-                            tx = %id,
-                            %key,
-                            subscriber_updated = %subscriber.peer(),
-                            "subscribe: updated subscriber address from transport source"
-                        );
-                    }
                     let own_loc = op_manager.ring.connection_manager.own_location();
 
                     if !matches!(