Expand description
Global KOE_ST form.
The public C++ implementation routes GLOBAL.KOE_ST to tnm_command_proc_koe,
and that command handler is a stub: it only returns the element itself when the
chain stops at KOE_ST, and otherwise treats the operation as unsupported.
Keep the Rust port aligned to that public source surface. Voice playback flows
through other script/UI paths, not through GLOBAL.KOE_ST commands here.