chore(pairing): trace which relays accepted each identity RPC

The Sep 23 08:59 live scan died at get_public_key with the subscribe race
already fixed, and a post-hoc relay sweep found neither our request nor
Amber's connect reply on any healthy pairing relay — the session lived on
damus.io (503-flapping) and nostr.band (handshake-hanger, still enabled in
user settings and therefore merged into the pairing set). publish_payload
now returns the accepting-relay list and send_rpc traces it for live
sessions (rpc published: method=… accepted_by=…, NONE when no relay took
the event), so the next scan names the dead relay instead of guessing.

src/signer/nip46_client.rs

@@ -1139,8 +1139,27 @@ impl Nip46ClientSigner {
                 .insert(id.clone(), PendingRemoteRequest { sender });
 
             let payload = json!({ "id": id, "method": method, "params": params }).to_string();
-            self.publish_payload(&client, &keys, &conversation, &peer, &payload)
+            match self
+                .publish_payload(&client, &keys, &conversation, &peer, &payload)
                 .await
+            {
+                Ok(accepted) => {
+                    if live_relays(&connection.relays) {
+                        pairing_trace(&format!(
+                            "rpc published: method={} id={} accepted_by={}",
+                            method,
+                            &id[..8],
+                            if accepted.is_empty() {
+                                "NONE".to_string()
+                            } else {
+                                accepted.join(",")
+                            }
+                        ));
+                    }
+                    Ok(())
+                }
+                Err(detail) => Err(detail),
+            }
         };
         if let Err(detail) = send_result {
             self.inner.lock().await.remote_pending.remove(&id);
@@ -1846,7 +1865,7 @@ impl Nip46ClientSigner {
         conversation: &ConversationKey,
         peer: &PublicKey,
         payload: &str,
-    ) -> Result<(), String> {
+    ) -> Result<Vec<String>, String> {
         let content = nip44_encrypt(conversation, payload).map_err(|e| e.message().to_string())?;
         let tag = Tag::parse(["p", peer.to_hex().as_str()]).map_err(|e| format!("{e}"))?;
         let event = EventBuilder::new(Kind::NostrConnect, content)
@@ -1854,11 +1873,11 @@ impl Nip46ClientSigner {
             .finalize_async(keys)
             .await
             .map_err(|e| format!("Could not sign: {e}"))?;
-        client
+        let output = client
             .send_event(&event)
             .await
             .map_err(|e| format!("{e}"))?;
-        Ok(())
+        Ok(output.success.keys().map(|u| u.to_string()).collect())
     }
 }