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/architecture.puml

@@ -0,0 +1,40 @@
+@startuml xui-deploy-architecture
+skinparam componentStyle rectangle
+skinparam defaultFontName Arial
+skinparam backgroundColor #FAFAFA
+
+package "xui-deploy Skill" {
+  component "SKILL.md\n(instructions)" as SKILL
+  component "evals/evals.json" as EVALS
+}
+
+package "Local Machine" {
+  component "SSH private key" as KEY
+  actor Developer
+}
+
+package "VPS (Linux)" {
+  component "curl / bash" as CURL
+  component "x-ui CLI\n(x-ui setting / restart)" as XUCLI
+  component "3x-ui Service\n(systemd)" as SERVICE
+  database "x-ui Data\n(/etc/x-ui/)" as DATA
+  component "Panel Web UI\n(:<panel_port>)" as PANEL
+  component "Firewall\n(ufw / firewalld)" as FW
+}
+
+cloud "GitHub" {
+  component "install.sh\n(MHSanaei/3x-ui)" as INSTALLER
+}
+
+Developer --> SKILL : triggers skill
+SKILL --> KEY : SSH auth
+SKILL --> CURL : runs installer via SSH
+CURL --> INSTALLER : downloads install.sh
+INSTALLER --> SERVICE : installs & starts
+SKILL --> XUCLI : configure port/user/pass/path
+XUCLI --> SERVICE : restart
+SERVICE --> DATA : persists config
+SERVICE --> PANEL : serves web UI
+SKILL --> FW : opens panel port
+SKILL --> Developer : reports panel URL
+@enduml