Read a rebuild of an unchanged source as no move, whatever image digest it made (hq issue 280)

An image is not byte-reproducible, so ADR 0236's 'same artifacts is no move'
never held for one: a catalogue merge that did not touch the bus rebuilt it,
and every send to the control node waited for a planned bus upgrade.

The builder now records a source fingerprint per build (module tree, context
trees, bases and toolchains by digest). A rebuild with the fingerprint of the
build it repeats is registered with that build's artifacts, handed to modules
standing on it, holds no push, demands no bus step, and a plan sends and
gates nothing for it. Identical artifacts remain a second way to be no move.

cmd/mesh-controller/build.go

@@ -148,6 +148,8 @@ func buildFrom(result link.BuildResult) inventory.Build {
 		// be, for exactly the modules it needs most. Keeping them is what makes a replay able to
 		// rebuild the graph rather than a list of names.
 		Path: result.Path,
+		// What it was made from (novox/hq issue 280): two builds with one are one build.
+		SourceFingerprint: result.SourceFingerprint,
 	}
 	// When it was asked, which is what orders it against another build of the same module
 	// (novox/hq 04-ISSUES/219) — not when it was heard.
@@ -580,6 +582,23 @@ func takeIn(ctx context.Context, inv *inventory.Inventory, result link.BuildResu
 			"back: it is recorded and not registered again — a newer build is", result.On, manifest.Module,
 			short(result.Commit))
 	}
+	// **A build whose source is unchanged is never a move** (novox/hq issue 280): a rebuild made from
+	// what the build the mesh stands on was made from registers that build's artifacts at the new
+	// commit, so no machine is sent a new digest for a source nobody changed — an image is not
+	// byte-reproducible, and the bus rebuilt for another module's merge demanded a planned upgrade.
+	if kept.SourceFingerprint != "" {
+		stands, raw, err := inv.StandingBuild(ctx, manifest.Module, kept.ID)
+		if err != nil {
+			return manifest, kept, err
+		}
+		if stands != "" && stands != kept.ID && len(raw) > 0 {
+			if same, err := catalogue.ParseManifest(raw); err == nil && same.Module == manifest.Module {
+				fmt.Printf("%s at %s was made from the source %s was: registered with its artifacts, no move\n",
+					manifest.Module, short(result.Commit), stands)
+				manifest = same
+			}
+		}
+	}
 	if err := inv.RegisterModule(ctx, manifest, recorded); err != nil {
 		if errors.Is(err, inventory.ErrSuperseded) {
 			return manifest, kept, fmt.Errorf("%s built %s (%s), recorded and not registered: %w",