Add snippets.d auto-import for modular config

SKILL.md

@@ -42,6 +42,17 @@ Create a `Caddyfile` in your skill's directory or set `CADDYFILE_PATH` environme
 # }
 ```
 
+## Auto-Import from Skills
+
+Other skills can drop `.caddy` snippets into `caddy/snippets.d/` and they'll be automatically merged at startup.
+
+Example: If `ttyd` skill is present with `TTYD_DOMAIN=terminal.example.com`, it creates:
+```
+caddy/snippets.d/ttyd.caddy
+```
+
+Caddy's `run.sh` merges all snippets into the config before starting.
+
 ## Usage
 
 This skill is typically used as a dependency by other skills that need a web server: