GHSA-9868-vxmx-w862: OpenClaw's system.run allowlist bypass via shell line-continuation command substitution

In OpenClaw system.run allowlist mode, shell-wrapper analysis could be bypassed by splitting command substitution as $\\ + newline + ( inside double quotes. Analysis treated the payload as allowlisted (for example /bin/echo), while shell runtime folded the line continuation into $(...) and executed non-allowlisted subcommands.