Fix workflow-lint CI failure from invalid temp workflow and shell argument expansion

[Copilot]

The GitHub Actions workflow lint job failed due to two workflow-shell issues: a broken quoted script in a temporary workflow file and unsafe unquoted expansion of LIBTEST_ARGS in ci.yml.

• Workflow cleanup

  • Removed .github/workflows/tmp_mac_test.yml, which contained a malformed multi-line run script that ShellCheck could not parse.

• Shell-safe argument handling in CI

  • Updated .github/workflows/ci.yml to parse optional LIBTEST_ARGS into a bash array and pass it with quoted array expansion, avoiding SC2086 while preserving multi-arg behavior.

  if [ -n "${LIBTEST_ARGS:-}" ]; then
    IFS=' ' read -r -a libtest_args <<< "${LIBTEST_ARGS}"
  else
    libtest_args=()
  fi
  
  cargo nextest run ... -- "${libtest_args[@]}"