Answer what the records keep, collect on a person's word, and name a machine's images (hq ADR 0251)

The store's tools and a machine's image pruning decide from the records, so
the controller says them: artifacts (every recorded artifact, kept and why,
eligible, collected on request), collect (the after-build sweep on demand,
a dry run unless confirmed with a why, recorded as a hand act) and images
(what a machine's declaration names, now and as last sent). The sweep is one
implementation with two sets of bounds.

internal/inventory/artifacts_test.go

@@ -0,0 +1,66 @@
+package inventory
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// **Every artifact made has one state, and a kept one says why** (novox/hq ADR 0251): what the
+// store's own tools set beside what the store holds, so an operator reads why something stays.
+func TestEveryArtifactMadeHasAStateAndAKeptOneSaysWhy(t *testing.T) {
+	inv := fresh(t)
+	ctx := context.Background()
+	var made []string
+	for i := 1; i <= 8; i++ {
+		made = append(made, built(t, inv, fmt.Sprintf("b%02d", i), "web", i))
+	}
+	// The definition names the oldest and the newest: the newest is kept for both reasons.
+	m := catalogue.Manifest{Module: "web", Version: "1", Resources: []map[string]any{
+		{"id": "app", "type": "container", "name": "web", "image": made[0]},
+		{"id": "next", "type": "container", "name": "web-next", "image": made[7]},
+	}}
+	if err := inv.RegisterModule(ctx, m, Source{Repository: "https://forge.invalid/web.git"}); err != nil {
+		t.Fatal(err)
+	}
+	if err := inv.MarkCollected(ctx, []string{made[1]}); err != nil {
+		t.Fatal(err)
+	}
+	states, err := inv.Artifacts(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(states) != len(made) {
+		t.Fatalf("%d states for %d artifacts made", len(states), len(made))
+	}
+	want := []struct {
+		state string
+		why   []string
+	}{
+		{ArtifactKept, []string{KeptByDefinition}},
+		{ArtifactCollected, nil},
+		{ArtifactEligible, nil},
+		{ArtifactKept, []string{KeptByRecentBuild}},
+		{ArtifactKept, []string{KeptByRecentBuild}},
+		{ArtifactKept, []string{KeptByRecentBuild}},
+		{ArtifactKept, []string{KeptByRecentBuild}},
+		{ArtifactKept, []string{KeptByRecentBuild, KeptByDefinition}},
+	}
+	for i, s := range states {
+		if s.Reference != made[i] {
+			t.Fatalf("state %d is of %s, want %s: the oldest first", i, s.Reference, made[i])
+		}
+		if s.State != want[i].state || fmt.Sprint(s.Why) != fmt.Sprint(want[i].why) {
+			t.Errorf("%s: %s %v, want %s %v", s.Reference, s.State, s.Why, want[i].state, want[i].why)
+		}
+	}
+	collect, err := inv.ToCollect(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(collect) != 1 || collect[0] != made[2] {
+		t.Errorf("ToCollect is %v, want only the eligible %s", collect, made[2])
+	}
+}