A gate judges its own send and the build it sent, and never puts the controller back behind its store (hq issue 352)

On 2026-10-09 a release's gate on the control node read the machine's
report against a newer send another plan had just made there, failed
three builds the machine had reported healthy, and put them back on
every machine to a controller older than the store's schema; that
controller then passed the newer plan's gate from its own health.

- A gate keeps what its send carried (digest, sequence) and reads the
  report against it; a report on the last send is on it too.
- A gate judges only the build the machine was last sent: another build
  there supersedes the judging — no verdict, nothing put back.
- A controller is told its build (MESH_CONTROLLER_VERSION, ${version}
  in a process's env) and records how far it reads the store's schema;
  a put-back to a build that reaches less, or never said, is refused
  and the current build kept, said as urgent.
- A release's open gate holds other sends of its modules there, and a
  plan's own first send waits on it.

cmd/mesh-controller/acting.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"strings"
 	"sync"
 	"time"
 
@@ -179,7 +180,21 @@ func (a *actor) release() {
 // holderOf is this process as the lease's holder.
 func holderOf(instance string) lease.Holder {
 	host, _ := os.Hostname()
-	return lease.Holder{Instance: instance, Host: host, Build: version}
+	build := runningBuild()
+	if build == "" {
+		build = version
+	}
+	return lease.Holder{Instance: instance, Host: host, Build: build}
+}
+
+// RunningBuildVar is where the declaration tells this process which build it is (module.json, the
+// controller process's env): the version its bundle is delivered as, `${version}` composed by the
+// catalogue from the bundle's digest. Empty for a process placed by hand.
+const RunningBuildVar = "MESH_CONTROLLER_VERSION"
+
+// runningBuild is the version of the build this process is, or empty when the declaration did not say.
+func runningBuild() string {
+	return strings.TrimSpace(os.Getenv(RunningBuildVar))
 }
 
 // serveUnderTheLease takes the lease for the serving controller, waiting while another holds it, and