Delete the builder, the build asks, the build queue and the merge gate: the builder's keys are the only way a module is built (issues 1851, 1299, 1318; C2b-C5, C10)

The controller asks no build of anybody (ADR 0501 §5, ADR 0525 clause 6, ADR 0503 §3). Every module of a walk is taken from the
builder's done key; a key not done yet waits, named in the plan, and never fails it.

- C2b/C2c: internal/builder and cmd/mesh-controller's asks go (askABuild, onlyTheBuildersOwn, buildOneAsked, takeIn from an
  outcome, buildAgentsOwn, the builder's say and its fallback, the daemon hearing an outcome). The server follows the retired
  seats' built subjects only to let go of them, because the installer's carried user list names them.
- C2d: replay, queue, cancel, clear, kill, pause, resume, delivery-check, check-here and merge-gate are refused by name.
- C3: the check queues (CHECKS_READY, CHECKS_OTHER) and their workers, the checks-running and plans-building buckets and
  their grants, the build queue and its hold (plans_building.go, queue.go, link/holds.go, builds_nats.go, checks_nats.go).
- C4: merge_gate*.go, the pull request's repo-check path, the Checked event and its layers; a pull request asks the
  controller nothing but to tell mesh-config what its head declares.
- C5: the builds bucket is written only by key_takein.
- C10 (help and refusals): the terminal's help lists only what is served.

Integration tests of the plan's tiers, sends, stops and retries now run on a stand-in builder with a done key for every
module (walk_keys_scaffold_integration_test.go); the tests of the asks, the queue, the merge gate and the replays are deleted.

cmd/mesh-controller/chain_integration_test.go

@@ -14,7 +14,6 @@ import (
 	"github.com/novox/mesh-controller/internal/chain"
 	"github.com/novox/mesh-controller/internal/inventory"
 	"github.com/novox/mesh-controller/internal/lease"
-	"github.com/novox/mesh-controller/internal/link"
 )
 
 // **Acceptance 10 of design 47: one read of an assignment names the commit, the build and the rollout that put it there,
@@ -80,7 +79,7 @@ func TestOneReadOfAnAssignmentNamesItsCommitBuildAndRolloutAndOneReadOfTheRollou
 	if err != nil {
 		t.Fatal(err)
 	}
-	for try := 0; try < 3 && (asking.Modules["notes"] == nil || asking.Modules["notes"].Build == ""); try++ {
+	for try := 0; try < 6 && (asking.Modules["notes"] == nil || asking.Modules["notes"].Build == "" || asking.Modules["notes"].State == "asked"); try++ {
 		advancePlans(ctx, open)
 		if asking, err = inv.PlanByID(ctx, rollout); err != nil {
 			t.Fatal(err)
@@ -90,13 +89,6 @@ func TestOneReadOfAnAssignmentNamesItsCommitBuildAndRolloutAndOneReadOfTheRollou
 	if buildID == "" || len(*asked) != 1 || !strings.HasSuffix((*asked)[0], "#"+buildID) {
 		t.Fatalf("the walk asked %v, and notes' build is %q", *asked, buildID)
 	}
-	digest := "sha256:" + strings.Repeat("a", 64)
-	result := outcome(buildID, "modules/notes", "c-notes", "notes", "")
-	result.ReuseKey = "rk-notes"
-	result.Made = []link.MadeArtifact{{Name: "notes", Kind: "image", Reference: "artifact-store://notes/notes@" + digest}}
-	if err := (builds{inv: inv, open: open}).Built(ctx, result); err != nil {
-		t.Fatal(err)
-	}
 
 	// The walk sends the tier to its first machine.
 	for try := 0; try < 3 && len(sent) == 0; try++ {
@@ -116,9 +108,9 @@ func TestOneReadOfAnAssignmentNamesItsCommitBuildAndRolloutAndOneReadOfTheRollou
 	if wireguard, pulled := assignmentOf(on, "mesh-wireguard"); pulled && (wireguard.Build != "" || wireguard.Rollout != "") {
 		t.Fatalf("a module this rollout did not send names a build or a rollout: %+v", wireguard)
 	}
-	if a.Module != "notes" || a.Commit != "c-notes" || a.Build != buildID || a.Rollout != rollout || a.Artifact != digest ||
+	if a.Module != "notes" || a.Commit != "c-notes" || a.Build != buildID || a.Rollout != rollout ||
 		a.Since.IsZero() || a.Assigned.IsZero() || !a.Stands() {
-		t.Fatalf("the assignment names %+v, not commit c-notes, build %s, artifact %s, rollout %s", a, buildID, digest, rollout)
+		t.Fatalf("the assignment names %+v, not commit c-notes, build %s, rollout %s", a, buildID, rollout)
 	}
 	// One read of the rollout.
 	p, err := inv.PlanByID(ctx, rollout)
@@ -130,16 +122,11 @@ func TestOneReadOfAnAssignmentNamesItsCommitBuildAndRolloutAndOneReadOfTheRollou
 		p.Steps[0].Node != "anchor" || p.Steps[0].Sent == nil {
 		t.Fatalf("the rollout lists changed %+v, builds %v, steps %+v; want %+v", p.Changed, p.Builds, p.Steps, wantChange)
 	}
-	// And one read of the build names the same commit, with what it published and its reuse key.
+	// And one read of the build names the same commit.
 	built, found, err := inv.BuildByID(ctx, buildID)
 	if err != nil || !found || built.Commit != "c-notes" || built.Module != "notes" {
 		t.Fatalf("the build: %+v %v %v", built, found, err)
 	}
-	lately, err := inv.Builds(ctx, "notes", 1)
-	if err != nil || len(lately) != 1 || lately[0].ReuseKey != "rk-notes" || lately[0].Published == nil ||
-		lately[0].Published.Artifact != digest {
-		t.Fatalf("what the build published: %+v %v", lately, err)
-	}
 	// The verbs say the links.
 	if lines := changedLines(p); len(lines) != 2 || !strings.Contains(lines[1], "anchor/notes") ||
 		!strings.Contains(lines[1], buildID) {