feat(caddy): add caddy_list_certs whitelist entry and cert parser

- Extend commands.yml.example with caddy_list_certs (sh loop over /data/caddy/certificates/*/*.crt using openssl)
- Add lib/parse-caddy.ts: parseCertList() parses CERTFILE/CERTEND delimited openssl output
- Add shiki ^1.29.2 dependency for server-side Caddyfile syntax highlighting

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ops-agent/commands.yml.example

@@ -63,3 +63,10 @@ commands:
   caddy_show_config:
     cmd: ["caddy", "fmt", "/etc/caddy/Caddyfile"]
     description: "Print the formatted Caddy config"
+
+  caddy_list_certs:
+    cmd:
+      - sh
+      - -c
+      - "for f in /data/caddy/certificates/*/*.crt; do [ -f \"$f\" ] || continue; echo \"CERTFILE:$f\"; openssl x509 -noout -subject -issuer -dates -in \"$f\" 2>&1; echo \"CERTEND\"; done"
+    description: "List TLS cert info (subject, issuer, validity dates) from Caddy certificate store"