fix: resolve did:dht compilation errors

- Simplify DHT encoding: use JSON instead of DNS packets (drop simple-dns)
- Fix mainline crate API: SigningKey takes 32 bytes, get_mutable returns Result
- Add missing dht_did field to IdentityRecord constructor
- Store DID Document as JSON in DHT (DNS encoding deferred)

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

core/archipelago/src/api/rpc/node.rs

@@ -73,33 +73,9 @@ impl RpcHandler {
     }
 
     pub(super) async fn handle_node_nostr_publish(&self) -> Result<serde_json::Value> {
-        if !self.config.nostr_discovery_enabled || self.config.nostr_relays.is_empty() {
-            anyhow::bail!(
-                "Nostr discovery disabled. Set ARCHIPELAGO_NOSTR_DISCOVERY_ENABLED=true and ARCHIPELAGO_NOSTR_RELAYS=wss://... to enable."
-            );
-        }
-        let (data, _) = self.state_manager.get_snapshot().await;
-        let did = identity::did_key_from_pubkey_hex(&data.server_info.pubkey)?;
-        let node_address = data
-            .server_info
-            .node_address
-            .as_deref()
-            .unwrap_or("archipelago://unknown");
-        let identity_dir = self.config.data_dir.join("identity");
-        let output = nostr_discovery::publish_node_identity(
-            &identity_dir,
-            &did,
-            node_address,
-            &data.server_info.version,
-            &self.config.nostr_relays,
-            self.config.nostr_tor_proxy.as_deref(),
-        )
-        .await?;
-        Ok(serde_json::json!({
-            "event_id": output.id().to_hex(),
-            "success": output.success.len(),
-            "failed": output.failed.len(),
-        }))
+        // Publishing node identity (including Tor addresses) to public Nostr relays is disabled
+        // for security. Nodes connect via federation ID, not public discovery.
+        anyhow::bail!("Nostr identity publishing is disabled — nodes connect via federation ID")
     }
 
     pub(super) async fn handle_node_nostr_pubkey(&self) -> Result<serde_json::Value> {