Judge each machine's report from its own send, so a first machine opens the gate

With one machine first a module is sent twice, and the tier gate asked every
machine for a report after the second send: the first machine's report, made
between the two, read as stale and the plan waited for ever (hq issue 256).
Also round a plan's wait to the second, not the minute, so it is not 0s.

cmd/mesh-controller/release_plan_test.go

@@ -181,3 +181,34 @@ func TestAPlanSettlesAnAskedBuildFromTheRecords(t *testing.T) {
 		t.Errorf("a recorded failure did not fail the plan: %+v %+v", q, q.Modules["x"])
 	}
 }
+
+// The first machine's report, made between the send to it and the send to the rest, opens the gate for it:
+// each machine is judged from its own send, not from the last one (novox/hq issue 256).
+func TestTheGateJudgesEachMachineFromItsOwnSend(t *testing.T) {
+	built := time.Date(2026, 10, 5, 18, 22, 0, 0, time.UTC)
+	firstSent := built.Add(31 * time.Second)
+	firstReported := built.Add(43 * time.Second)
+	restSent := built.Add(58 * time.Second)
+	restReported := built.Add(74 * time.Second)
+	reports := []inventory.Reported{
+		{Node: "ace", At: &firstReported},
+		{Node: "g14", At: &restReported},
+	}
+	since := func(node string) time.Time {
+		if node == "ace" {
+			return firstSent
+		}
+		return restSent
+	}
+	if ok, waiting := appliedEach("build-agent", since, []string{"ace", "g14"}, reports); !ok {
+		t.Fatalf("the gate still waits on %v, though each reported after its own send", waiting)
+	}
+	// The old reading, every machine from the last send, is what held the plan.
+	if ok, _ := applied("build-agent", restSent, []string{"ace", "g14"}, reports); ok {
+		t.Fatal("the single-moment reading should hold the first machine back")
+	}
+	early := built.Add(10 * time.Second)
+	if ok, waiting := appliedEach("build-agent", since, []string{"ace"}, []inventory.Reported{{Node: "ace", At: &early}}); ok || waiting[0] != "ace" {
+		t.Fatal("a report from before the machine was sent opened the gate")
+	}
+}