Drop the descriptor Default of 60 so the global panel field can be left
blank. A non-blank global value sits at the top of the cascade and locks
every lower layer, so the fixed default made the per-minute limit
un-overridable by organizations and users. Blank now means "inherit";
the runtime still falls back to 60 when no layer sets a value, so the
usage gauge is unchanged. Update the descriptor help and the Settings
row copy to explain the inherit behavior.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
