Build modules run at most as many steps as their node's build CPU gives, and say a check's phases

Each of mesh-build-go, -node and -image declares cores-per-step (6, 2, 2) and hands it to the
SDK puller, which bounds the configured capacity by floor(slice quota cores / cores-per-step),
read live; thread limits and the status tools follow the effective capacity (issue 1806's
follow-up: three Go checks on shanks' 12-core slice starved past the 30-minute step bound).
mesh-build-go says its lint and test phases with the ask id (issue 1890).

modules/mesh-build-node/cmd/mesh-build-node/asks.go

@@ -48,9 +48,13 @@ func (m *Module) Puller(steps []StepTool, source buildstep.AskSource) *buildstep
 	// The capacity's own change wakes the puller (issue 1887): the runtime's watch of the config value as mesh-config
 	// resolved it; the settings file is read only when that watch cannot start. A test's Capacity is its own.
 	var watch func(string, func(stdio.ProvisionChange) error) error
+	// And the CPU bounds it (issue 1806's follow-up): the configured capacity is an upper bound, the node's build slice
+	// gives floor(its quota's cores / the module's cores-per-step) at once, read live; a test judges by its own Capacity.
+	var cores func() float64
 	if capacity == nil {
 		capacity = buildstep.NodeCapacity(m.Settings, buildstep.DefaultCapacities, m.Node, m.Say)
 		watch = buildstep.WatchConfigServed
+		cores = buildstep.NodeCoresPerStep(m.Settings, buildstep.DefaultCoresPerStep[delivery.AskNode], m.Say)
 	}
 	ask := m.askSteps(steps)
 	var load func(string) ([]byte, error)
@@ -58,7 +62,7 @@ func (m *Module) Puller(steps []StepTool, source buildstep.AskSource) *buildstep
 		load = func(key string) ([]byte, error) { return m.ReadPauses.Get(key) }
 	}
 	return &buildstep.Puller{Source: source, Language: delivery.AskNode, Node: m.Node, Put: m.Steps, PausePut: m.Pauses, Load: load,
-		Capacity: capacity, WatchConfig: watch, Logf: m.Say,
+		Capacity: capacity, WatchConfig: watch, CoresPerStep: cores, Logf: m.Say,
 		Run: func(ctx context.Context, a delivery.StepAsk) (any, error) {
 			if err := m.Prepare(ctx); err != nil {
 				return nil, err