The node-engine follows the module-assignment seat: assignments, not placement; the seat's packages move to mesh-contracts and mesh-delivery (issue 1966)

The state, events and types of the seat mesh-module-assigner say assignments; the legacy node key form is gone from the
reads; the dead seat-verb list of the retired name is deleted. The placement guard and the placed-file sense stay.

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

internal/compose/fromruntime/fromruntime.go

@@ -34,7 +34,7 @@ func (States) Keys(state string) ([]string, error) { return stdio.State(state).K
 func Reader() frombus.Reader { return frombus.StatesReader(States{}, HTTPFetch) }
 
 // Watched is frombus's States over a watched copy (novox/hq ADR 0580 clause 1): the states a composition reads whole
-// (placement, haves, modules, resolved values) from the copy, a build by key when asked, a manifest once per digest.
+// (assignment, haves, modules, resolved values) from the copy, a build by key when asked, a manifest once per digest.
 type Watched struct{ *stdio.WatchedStates }
 
 // Get is a key's value: a build read now, a manifest kept once read, any other state's from the copy.