G.5:4.3 - Selector head and narrower selector families

Selection and dispatch stay one generic selector head. Narrower selector families may refine it, but they do not redefine the universal invariants pinned through G.Core, do not add new mandatory inputs to inherited Select, and do not mutate inherited SlotKinds. Required policy and edition refs use the declared input meanings.

Method- and generator-specific pressures such as QD archives, open-ended declared sets, explore and exploit lenses, or preference comparators do not become part of the selector head. They arrive only through explicit extension declarations and the pins those extensions require.