feat: add xui-deploy skill with lessons learned

- SKILL.md v1.1: full deployment workflow for 3x-ui on VPS via SSH
- Covers Docker/native install, Nginx+TLS, Xray inbound config
- references/xray-inbound-config.md: VLESS+WS+TLS and Reality configs
- references/lessons-learned.md: lessons from first real deployment
  - /app/x-ui binary vs shell wrapper in Docker
  - correct API path: panel/api/inbounds/add
  - subPath-only DB write (subURI causes blank settings page)
  - --network host port exposure workaround
- Agent prompt and eval configs included

skills/xui-deploy/assets/workflow.puml

@@ -0,0 +1,43 @@
+@startuml xui-deploy-workflow
+skinparam defaultFontName Arial
+skinparam backgroundColor #FAFAFA
+
+actor Developer
+participant "xui-deploy\nSkill" as SKILL
+participant "VPS (SSH)" as VPS
+participant "GitHub\n(install.sh)" as GH
+
+Developer -> SKILL : deploy x-ui on VPS
+SKILL -> Developer : collect host, SSH user, key, panel password
+
+SKILL -> VPS : ssh echo OK (connectivity test)
+alt SSH fails
+  SKILL -> Developer : report error, stop
+end
+
+SKILL -> VPS : cat /etc/os-release
+alt unsupported OS
+  SKILL -> Developer : warn, ask to confirm
+end
+
+SKILL -> VPS : curl install.sh | bash
+VPS -> GH : download install.sh
+alt x-ui already installed
+  VPS -> VPS : update to latest version
+else fresh install
+  VPS -> VPS : install 3x-ui + systemd service
+end
+
+SKILL -> VPS : x-ui setting -port / -username / -password / -webBasePath
+SKILL -> VPS : x-ui restart
+SKILL -> VPS : x-ui status
+
+alt service not running
+  SKILL -> VPS : x-ui log (last 30 lines)
+  SKILL -> Developer : report error
+end
+
+SKILL -> VPS : ufw allow <port> OR firewall-cmd --add-port
+
+SKILL -> Developer : panel URL + username + version
+@enduml