Add smart Caddy auto-configuration

SKILL.md

@@ -29,6 +29,7 @@ Installs [ttyd](https://github.com/tsl0922/ttyd) - a simple command-line tool fo
 | `TTYD_COMMAND` | Command to run | `/bin/bash` |
 | `TTYD_CREDENTIAL` | Basic auth (user:pass) | (none) |
 | `TTYD_OPTIONS` | Additional ttyd options | (none) |
+| `TTYD_DOMAIN` | Domain for Caddy auto-config | (none) |
 
 ## Usage
 
@@ -54,7 +55,20 @@ TTYD_CREDENTIAL="admin:secret" ./scripts/run.sh
 TTYD_COMMAND="htop" ./scripts/run.sh
 ```
 
-### With Caddy (HTTPS)
+### Auto-configuration with Caddy
+
+If the `caddy` skill is present, ttyd will automatically register itself:
+
+```bash
+# Set domain for auto-config
+TTYD_DOMAIN="terminal.example.com"
+```
+
+This creates a snippet in `caddy/snippets.d/ttyd.caddy` that Caddy imports on startup.
+
+### Manual Caddy Config
+
+If not using auto-config:
 
 ```caddyfile
 terminal.example.com {