Follow-up hints for the references tool, keyed off the hint_context maps
YmerNode.Mcp.Tools.References.Actions produces.
Only add and update steer. After them the natural next step is viewing the
reference — and that includes the duplicate-add path, where the steer to the
EXISTING reference is the response's whole point. Every other action emits
nothing: find and list results already carry each reference's derived source
and, where one is derivable, its recipe; a read or refresh answer carries
the entry's age and where the next window starts; and watch answers the
watch itself — a hint on any of them would be noise on a response that is
already complete.