D2 (view): build_usage reads the build seats' steps and pauses as seat reads in the holder's state

The manifest reads seat:<seat>.steps and .pauses, which the grants part resolves, and the tools read <holder>.steps and <holder>.pauses.

Builds: design 47 G A-82, A-128

Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h

modules/mesh-delivery-view/cmd/mesh-delivery-view-tools/main.go

@@ -422,6 +422,21 @@ func holderOf(ask func(key string, body any) (json.RawMessage, error)) func(seat
 	}
 }
 
+// ofHolder reads a build seat's state (`steps`, `pauses`) in the state of the seat's holder, `<holder>.<state>`, the holder found
+// as seatlist.HolderOf finds it (design 47 G A-128, A-126), as the manifest's `seat:<seat>.<state>` reads name it: the grants
+// part resolves a read only in that form. A seat whose holder cannot be found reads as an error naming it.
+func ofHolder(holder func(seat string) (string, bool), read func(name string) view.StateRead, state string) func(seat string) view.StateRead {
+	return func(seat string) view.StateRead {
+		module, ok := holder(seat)
+		if !ok {
+			fail := fmt.Errorf("the holder of %s is not found", seat)
+			return view.StateRead{Keys: func() ([]string, error) { return nil, fail },
+				Get: func(string) (json.RawMessage, error) { return nil, fail }}
+		}
+		return read(module + "." + state)
+	}
+}
+
 func main() {
 	logf := func(f string, a ...any) { fmt.Fprintf(os.Stderr, "[mesh-delivery-view-tools] "+f+"\n", a...) }
 	// The catalog half per watched branch, followed by the bundle itself through meshcatalogclient's branch follower on
@@ -463,8 +478,8 @@ func main() {
 	}, holderOf(stdio.Ask))
 	u := view.UsageReader{Haves: r.HavesState, Resolved: read(stdio.State("mesh-config.resolved")), Tries: read(stdio.State("mesh-delivery-checker.tries")),
 		Seats:    seats,
-		StepsOf:  func(seat string) view.StateRead { return read(stdio.State(seat + "." + view.StepsState)) },
-		PausesOf: func(seat string) view.StateRead { return read(stdio.State(seat + "." + buildstep.PausesState)) },
+		StepsOf:  ofHolder(holderOf(stdio.Ask), func(name string) view.StateRead { return read(stdio.State(name)) }, view.StepsState),
+		PausesOf: ofHolder(holderOf(stdio.Ask), func(name string) view.StateRead { return read(stdio.State(name)) }, buildstep.PausesState),
 		Backlog:  backlogOf(socket())}
 	// view_first_views and view_first_view_again: where the view's process stands with its first views of the indexer's and
 	// the assigner's states (ADR 0615 §6), and a re-read by hand.

modules/mesh-delivery-view/cmd/mesh-delivery-view-tools/main_test.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"mesh-delivery-view/internal/view"
 	"reflect"
+	"slices"
 	"strings"
 	"sync/atomic"
 	"testing"
@@ -650,3 +651,22 @@ func TestABuildSeatsHolderIsTheOneTheSeatListNames(t *testing.T) {
 		t.Error("a seat list that cannot be read names a holder")
 	}
 }
+
+// A build seat's steps and pauses are read in the state of the seat's holder, `<holder>.steps` and `<holder>.pauses`, the form
+// the manifest's `seat:<seat>.<state>` reads name and the grants part resolves (design 47 G A-82, A-128), never the seat's own name.
+func TestBuildSeatStatesAreReadInTheHoldersState(t *testing.T) {
+	var named []string
+	read := func(name string) view.StateRead {
+		named = append(named, name)
+		return view.StateRead{Keys: func() ([]string, error) { return nil, nil }}
+	}
+	holder := func(seat string) (string, bool) { return "acme-" + seat, seat != "node-build-node" }
+	ofHolder(holder, read, view.StepsState)("node-build-go")
+	ofHolder(holder, read, "pauses")("node-build-go")
+	if want := []string{"acme-node-build-go.steps", "acme-node-build-go.pauses"}; !slices.Equal(named, want) {
+		t.Errorf("read %v, want %v", named, want)
+	}
+	if _, err := ofHolder(holder, read, view.StepsState)("node-build-node").Keys(); err == nil {
+		t.Error("a seat with no holder reads without an error")
+	}
+}

modules/mesh-delivery-view/manifest_test.go

@@ -153,7 +153,7 @@ func TestManifestIsTakenAndReadsOnly(t *testing.T) { // 1134/AC7
 	if m.Module != "mesh-delivery-view" {
 		t.Errorf("module = %q", m.Module)
 	}
-	want := []string{"mesh-conditions.conditions", "mesh-config.resolved", "mesh-delivery-builder.build-log", "mesh-delivery-builder.builds", "mesh-delivery-checker.tries", "mesh-delivery-watchman.presence", "mesh-delivery-watchman.stuck", "mesh-healers.attempts", "mesh-provisioner.provisions", "mesh-vault.signers", "node-build-go.pauses", "node-build-go.steps", "node-build-image.pauses", "node-build-image.steps", "node-build-node.pauses", "node-build-node.steps", "node-engine.have"} // the build seats' states by seat, never a build module (design 47 G A-82); no read of the gate's source: each watched branch's is its verb source's (§512, A-173); // no reads of the indexer's or the assigner's states (ADR 0615 §1, DLV-M4); view_tiers reads the module graph and the provisioner's keys (ADR 0603 §6); view_status reads the keeper's conditions and the healers' attempts (1952/V1); build_usage reads the build modules' steps and pauses, mesh-config's capacities and the checker's tries; 1168/AC1, 1241/AC4, 1345/AC3, 1297/B8, B9
+	want := []string{"mesh-conditions.conditions", "mesh-config.resolved", "mesh-delivery-builder.build-log", "mesh-delivery-builder.builds", "mesh-delivery-checker.tries", "mesh-delivery-watchman.presence", "mesh-delivery-watchman.stuck", "mesh-healers.attempts", "mesh-provisioner.provisions", "mesh-vault.signers", "node-engine.have", "seat:node-build-go.pauses", "seat:node-build-go.steps", "seat:node-build-image.pauses", "seat:node-build-image.steps", "seat:node-build-node.pauses", "seat:node-build-node.steps"} // the build seats' states by seat, never a build module (design 47 G A-82); no read of the gate's source: each watched branch's is its verb source's (§512, A-173); // no reads of the indexer's or the assigner's states (ADR 0615 §1, DLV-M4); view_tiers reads the module graph and the provisioner's keys (ADR 0603 §6); view_status reads the keeper's conditions and the healers' attempts (1952/V1); build_usage reads the build modules' steps and pauses, mesh-config's capacities and the checker's tries; 1168/AC1, 1241/AC4, 1345/AC3, 1297/B8, B9
 	got := slices.Clone(m.Reads)
 	slices.Sort(got)
 	if !reflect.DeepEqual(got, want) {

modules/mesh-delivery-view/module.json

@@ -121,12 +121,12 @@
     "seat:node-engine.manifest-reads"
   ],
   "reads": [
-    "node-build-go.pauses",
-    "node-build-go.steps",
-    "node-build-image.pauses",
-    "node-build-image.steps",
-    "node-build-node.pauses",
-    "node-build-node.steps",
+    "seat:node-build-go.pauses",
+    "seat:node-build-go.steps",
+    "seat:node-build-image.pauses",
+    "seat:node-build-image.steps",
+    "seat:node-build-node.pauses",
+    "seat:node-build-node.steps",
     "mesh-config.resolved",
     "mesh-delivery-builder.build-log",
     "mesh-delivery-builder.builds",