Add PVE script-creator agent; remove legacy scripts

Add a new .github agent (pve-script-creator.agent.md) with workflow and strict rules for generating CT/install/json files. Remove legacy CT/install/json artifacts for alpine-ironclaw and openthread-br (ct/, install/, json/ entries deleted). Also adjust mqttx update logic: set CLEAN_INSTALL=1 and move the update msg_info after fetch_and_deploy_gh_release to ensure a clean deployment before reporting/updating and then run yarn build in the app web dir.

tools/addon/mqttx.sh

@@ -105,8 +105,9 @@ function uninstall_mqttx() {
 
 function update_mqttx() {
   if check_for_gh_release "mqttx" "$REPO"; then
-    msg_info "Updating ${APP}"
     CLEAN_INSTALL=1 fetch_and_deploy_gh_release "mqttx" "$REPO" "tarball" "latest" "$APP_DIR"
+
+    msg_info "Updating ${APP}"
     cd "$APP_DIR/web"
     $STD yarn install --frozen-lockfile --ignore-engines
     $STD yarn build