Optional descriptionWhat a hierarchical manager reads about the seat; without it the manager sees "General purpose".
Optional dependsSeats this one waits for under the graph strategy. An agency that names no strategy and is not adaptive
runs graph when any seat's dependsOn lists a seat; an empty list lists none. agency() throws
AgencyConfigError, naming the seat, for a dependsOn that is set and is not an array of seat names.
What a pre-built roster member may carry for the strategies, which read it as they read a seat config's: the hierarchical manager reads
descriptioninto its roster, and the graph strategy readsdependsOn.sessionSeat()sets both on the seat it returns.