H1 (review r2): the foundation host is the entry that claims the seat node-engine, not a module named mesh-host

Builds: design 47 G §527, §634

internal/compose/resolution/seat_dependencies.go

@@ -29,6 +29,10 @@ var appliedThrough = map[string]string{
 // A variable rather than a constant only so a test can hold both behaviours; nothing else sets it.
 var enforceSeatDependencies = true
 
+// nodeEngineSeat is the seat the node-engine's own module claims (design 47 G §508, §527, §634): the
+// foundation's host is the entry that claims it, never a module named here.
+const nodeEngineSeat = "node-engine"
+
 // foundationModules are the pieces genesis lays before any module exists (novox/hq ADR 0207 §5):
 // the host and the private network. Registered as modules so they can be assigned, but what they
 // declare is the installation's, not a module's, so it is never judged. The third piece, the
@@ -38,7 +42,6 @@ var enforceSeatDependencies = true
 // The private network's module is overlay.Name, written out because the overlay package composes
 // on top of this one; its resources are computed, which exempts it by the rule below as well.
 var foundationModules = map[string]bool{
-	"mesh-host":      true,
 	"mesh-wireguard": true,
 }
 
@@ -46,7 +49,7 @@ var foundationModules = map[string]bool{
 // module whose resources are computed is the mesh's by construction — the private network's peer
 // list and its tools are the controller's, written per node — so it counts whatever its name.
 func isFoundation(m mcat.Manifest) bool {
-	return foundationModules[m.Module] || m.Computed != ""
+	return foundationModules[m.Module] || m.ClaimsSeat(nodeEngineSeat) || m.Computed != ""
 }
 
 // DependsOn is every seat a module needs held on its node: derived from the resource types it

internal/compose/resolution/seat_dependencies_test.go

@@ -95,3 +95,17 @@ func TestWithTheSwitchFlippedAnUnmetDependencyRefusesTheNode(t *testing.T) {
 		t.Errorf("the first pass refused an unmet dependency: %v", err)
 	}
 }
+
+func TestTheFoundationHostIsTheEntryThatClaimsTheNodeEngineSeat(t *testing.T) {
+	svc := res("service", "x")
+	// Whatever its name, the entry claiming the seat is the foundation's: nothing to depend on.
+	engine := withResources(mod("the-engine", nil, nil, nil, mcat.Claim{Name: "node-engine"}), svc)
+	if got := DependsOn(nil, engine); len(got) != 0 {
+		t.Errorf("the entry claiming node-engine depends on %v, want nothing (§527)", got)
+	}
+	// A module named as the old code named the engine, claiming no such seat, is an ordinary module.
+	named := withResources(mod("mesh-host", nil, nil, nil), svc)
+	if got := DependsOn(nil, named); !reflect.DeepEqual(got, []string{mcat.ServiceManagerSeat}) {
+		t.Errorf("a module merely named mesh-host depends on %v, want the service manager seat", got)
+	}
+}