Area 4 (join 11): buildstep reads no bus, not even through buscalls

The builder's published package reached the bus library through buildstep,
whose KeptBuildsOf took mesh-sdk's buscalls.ObjectInfo, and buscalls now
imports nats.go for its seat chunks. buildstep's layouts, keys and codecs
are read by modules that never touch the bus (its own guard), so the kept
build of one object is judged from the object's own fields (KeptBuildOf,
SortKept) and the build module lists its store itself. The guard now also
refuses a bus library reached through an import, the kind that let this in.

Builds: design 47 G (join 11 area 4: builds TestThePackageReachesNoBus, buildstep's bus-free guard)

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

modules/mesh-delivery-sdk/buildstep/ask_test.go

@@ -11,7 +11,6 @@ import (
 	"testing"
 	"time"
 
-	"git.novox.be/novox/mesh-sdk/go/buscalls"
 	"git.novox.be/novox/mesh-sdk/go/catalogue"
 )
 
@@ -350,9 +349,17 @@ func TestDeclinesNeedsAndLevelDigest(t *testing.T) {
 		hex := strings.Repeat("a", 64)
 		name, desc := KeptObject(KeptFor{Module: "demo", Fp: "fp1"}, "ace", "sha256:"+hex)
 		at := time.Date(2026, 11, 10, 10, 0, 0, 0, time.UTC)
-		kept := KeptBuildsOf([]buscalls.ObjectInfo{{Name: name, Size: 9, Description: desc, Modified: at},
-			{Name: "bb", Description: `{"module":"demo","fp":"fp1","node":"g14"}`}}, "ace")
-		if len(kept) != 1 || kept[0].Digest != hex || kept[0].Bytes != 9 {
+		var kept []KeptBuild
+		for _, o := range []struct {
+			name, desc string
+			size       uint64
+		}{{"cc", `{"module":"demo","fp":"fp0","node":"ace"}`, 1}, {name, desc, 9}, {"bb", `{"module":"demo","fp":"fp1","node":"g14"}`, 3}, {"dd", "not json", 4}} {
+			if k, ok := KeptBuildOf(o.name, o.desc, o.size, at, "ace"); ok {
+				kept = append(kept, k)
+			}
+		}
+		SortKept(kept)
+		if len(kept) != 2 || kept[0].Digest != hex || kept[0].Bytes != 9 || !kept[0].LastUsed.Equal(at) || kept[1].Digest != "cc" {
 			t.Fatalf("kept on ace: %+v", kept)
 		}
 		claims := func(m string) (bool, error) {

modules/mesh-delivery-sdk/buildstep/busfree_test.go

@@ -3,6 +3,7 @@ package buildstep
 import (
 	"go/parser"
 	"go/token"
+	"os/exec"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -30,4 +31,15 @@ func TestThePackageIsFreeOfTheBus(t *testing.T) {
 			}
 		}
 	}
+	// Nor through a package it imports: a mesh-sdk package that came to import the bus library (buscalls' seat chunks) took
+	// the builder's published package onto the bus through this one (join 11).
+	out, err := exec.Command("go", "list", "-deps", ".").Output()
+	if err != nil {
+		t.Fatalf("go list: %v", err)
+	}
+	for _, p := range strings.Fields(string(out)) {
+		if strings.HasPrefix(p, "github.com/nats-io/") {
+			t.Errorf("buildstep depends on %s", p)
+		}
+	}
 }

modules/mesh-delivery-sdk/buildstep/keptartifact.go

@@ -7,7 +7,6 @@ import (
 	"strings"
 	"time"
 
-	"git.novox.be/novox/mesh-sdk/go/buscalls"
 	"git.novox.be/novox/mesh-sdk/go/catalogue"
 )
 
@@ -60,19 +59,20 @@ func KeptObject(k KeptFor, node, digest string) (name, description string) {
 	return strings.TrimPrefix(digest, "sha256:"), string(desc)
 }
 
-// KeptBuildsOf are the builds node keeps among a store's objects, by digest.
-func KeptBuildsOf(infos []buscalls.ObjectInfo, node string) []KeptBuild {
-	out := []KeptBuild{}
-	for _, i := range infos {
-		var k KeptBuild
-		if i.Deleted || json.Unmarshal([]byte(i.Description), &k) != nil || k.Node != node {
-			continue
-		}
-		k.Digest, k.Bytes, k.LastUsed = i.Name, i.Size, i.Modified.UTC()
-		out = append(out, k)
+// KeptBuildOf is the build node keeps under one object of a store, by its name (the digest), description, size and last change,
+// or false when the object names none of node's. The object's form is the build module's store's: this package reads no bus.
+func KeptBuildOf(name, description string, size uint64, modified time.Time, node string) (KeptBuild, bool) {
+	var k KeptBuild
+	if json.Unmarshal([]byte(description), &k) != nil || k.Node != node {
+		return KeptBuild{}, false
 	}
-	slices.SortFunc(out, func(a, b KeptBuild) int { return strings.Compare(a.Digest, b.Digest) })
-	return out
+	k.Digest, k.Bytes, k.LastUsed = name, size, modified.UTC()
+	return k, true
+}
+
+// SortKept orders kept builds by digest, the order kept-artifact's readers list them in.
+func SortKept(kept []KeptBuild) {
+	slices.SortFunc(kept, func(a, b KeptBuild) int { return strings.Compare(a.Digest, b.Digest) })
 }
 
 // ClaimsStoreOf reads the seat mesh-catalog's answer of one module (CatalogModuleVerb): whether its manifest claims the