fix: resolve shellcheck warnings (SC2168, SC2089, SC2090, SC2016, SC2329)

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

setup/configure_runners.sh

@@ -447,7 +447,6 @@ for ((i = 0; i < runner_count; i++)); do
   if [[ -z "$repos_default" ]]; then repos_default="all"; fi
   # Build hint with known repo names
   repos_hint="token scope: all"
-  local _rn
   for _rn in ${REPO_NAMES:-}; do
     repos_hint="${repos_hint}, ${_rn}"
   done