fix(identity): Node npub in Web5 Identities matches Settings (#49)

Settings shows the node-level Nostr key (HKDF derive_node_nostr_key,
read via node.nostr-pubkey) while Web5 > Identities showed the identity
record's own key — the mirrored "Node" identity stores nostr=None and
seed identities use a different BIP-32 NIP-06 key, so the two surfaces
disagreed.

Resolve the node-level Nostr key once in identity.list and override it
onto whichever identity record is the node's own (ed25519 == server_info
.pubkey). Display-only — no stored key is rewritten, so it self-applies
to existing nodes with no migration and the discovery identity is
unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

core/archipelago/src/api/rpc/identity/handlers.rs

@@ -14,10 +14,39 @@ impl RpcHandler {
         let manager = IdentityManager::new(&self.config.data_dir).await?;
         let (identities, default_id) = manager.list().await?;
 
+        // #49: The canonical node Nostr key is the node-level HKDF key
+        // (`derive_node_nostr_key`) that Settings and Nostr discovery both use
+        // via `node.nostr-pubkey`. The mirrored "Node" identity stores
+        // nostr=None, and seed identities use a different BIP-32 NIP-06 key, so
+        // the "Node" entry in Web5 > Identities disagreed with Settings. Resolve
+        // the node-level key once and override it onto whichever identity record
+        // is the node's own (its ed25519 matches `server_info.pubkey`), so both
+        // surfaces always show the same npub. Display-only — no key is rewritten.
+        let identity_dir = self.config.data_dir.join("identity");
+        let node_nostr_hex = crate::nostr_discovery::get_nostr_pubkey(&identity_dir)
+            .await
+            .ok();
+        let node_nostr_npub = node_nostr_hex.as_ref().and_then(|h| {
+            nostr_sdk::PublicKey::from_hex(h)
+                .ok()
+                .and_then(|pk| pk.to_bech32().ok())
+        });
+        let (snapshot, _) = self.state_manager.get_snapshot().await;
+        let node_pubkey_hex = snapshot.server_info.pubkey.clone();
+
         let items: Vec<serde_json::Value> = identities
             .into_iter()
             .map(|id| {
                 let is_default = default_id.as_deref() == Some(&id.id);
+                let is_node = !node_pubkey_hex.is_empty() && id.pubkey_hex == node_pubkey_hex;
+                let (nostr_pubkey, nostr_npub) = if is_node {
+                    (
+                        node_nostr_hex.clone().or(id.nostr_pubkey),
+                        node_nostr_npub.clone().or(id.nostr_npub),
+                    )
+                } else {
+                    (id.nostr_pubkey, id.nostr_npub)
+                };
                 serde_json::json!({
                     "id": id.id,
                     "name": id.name,
@@ -26,8 +55,8 @@ impl RpcHandler {
                     "did": id.did,
                     "created_at": id.created_at,
                     "is_default": is_default,
-                    "nostr_pubkey": id.nostr_pubkey,
+                    "nostr_pubkey": nostr_pubkey,
-                    "nostr_npub": id.nostr_npub,
+                    "nostr_npub": nostr_npub,
                     "profile": id.profile,
                 })
             })