feat: DID persistence + federation node names in sync

Part 1 — DID Persistence:
- Deploy script creates /var/lib/archipelago/identity/ directory
- First-boot script creates identity dir with proper ownership
- Identity load now logs pubkey to confirm persistence across restarts

Part 2 — Node Names:
- NodeStateSnapshot includes node_name field
- build_local_state() passes server name to sync responses
- update_node_state() stores peer's announced name on the FederatedNode
- Names propagate automatically during federation.sync-state

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

scripts/deploy-to-target.sh

@@ -678,9 +678,10 @@ PYEOF
       sudo mkdir -p /var/lib/archipelago/dwn/protocols
       sudo mkdir -p /var/lib/archipelago/content/files
       sudo mkdir -p /var/lib/archipelago/federation
+      sudo mkdir -p /var/lib/archipelago/identity
       sudo mkdir -p /var/lib/archipelago/identities
       sudo mkdir -p /var/lib/archipelago/tor-config
-      sudo chown -R archipelago:archipelago /var/lib/archipelago/dwn /var/lib/archipelago/content /var/lib/archipelago/federation /var/lib/archipelago/identities /var/lib/archipelago/tor-config 2>/dev/null || true
+      sudo chown -R archipelago:archipelago /var/lib/archipelago/dwn /var/lib/archipelago/content /var/lib/archipelago/federation /var/lib/archipelago/identity /var/lib/archipelago/identities /var/lib/archipelago/tor-config 2>/dev/null || true
       # Fix secrets directory ownership (must be readable by archipelago user, not root)
       sudo chown -R archipelago:archipelago /var/lib/archipelago/secrets 2>/dev/null || true
       sudo chmod 700 /var/lib/archipelago/secrets 2>/dev/null || true