S1-S3: the node-engine seat's client asks a node once more when an ask came while one ran, and shows when the event was heard (issue 1966 note 170)

An event of manifest-reads-changed heard while an ask of the same node ran was dropped
without a line, so a restated engine could stay read at its first statement (ace,
2026-11-10 07:36). Every reader goes through Keeper.AskNode, so the assigner, the
builder and the indexer are fixed at once (ADR 0668 §4: the caller hears it and calls
again; ADR 0634 §1: the seat's client).

- AskNode: an ask while one runs is asked once more after it, one follow-up however
  many came, said in one line (1966/AC170-1, AC170-3). The asks of one node so run one
  after another, and take keeps the last answer, as before (no rule on the engine's
  clock: review round 1).
- Statement.EventAt (event-at): when the node's event was last heard, read by the
  parts' engine-reads tools; forgotten with the node's key.

Claude-Session: https://claude.ai/code/session_01JG73KEq4zoDfM9WtYpcQgZ

go/clients/nodeengineclient/enginereads/enginereads_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"strings"
 	"testing"
 	"time"
@@ -95,6 +96,41 @@ func TestTheAnswerAndTheEventAreJudged(t *testing.T) {
 	if got := u.Unanswered([]string{"ace"}, heard, 5*time.Minute, clock); len(got) != 0 || !u.Statements()["ace"].UnansweredSince.IsZero() {
 		t.Errorf("an answered node is unanswered: %v", got)
 	}
+	// Issue 1966 note 170, 1966/AC170-1 and AC170-3: an event of a node heard while an ask of it runs is not dropped: the
+	// node is asked once more after that ask ends (one follow-up however many came), said in one line, and the newer
+	// statement is kept; the event's time is shown beside the statement (event-at).
+	const stated26, restated = "2026-11-10T07:36:26Z", "2026-11-10T07:36:30Z"
+	var lines []string
+	eclock := time.Date(2026, 11, 10, 7, 36, 26, 0, time.UTC)
+	asks := 0
+	var e *Keeper
+	e = &Keeper{Sync: true, Now: func() time.Time { return eclock },
+		Logf: func(f string, a ...any) { lines = append(lines, fmt.Sprintf(f, a...)) },
+		Put:  func(_ string, raw []byte) error { _, err := Decode(raw); return err },
+		Call: func(node, _ string, _ any) (json.RawMessage, error) {
+			asks++
+			stated := restated
+			if asks == 1 {
+				eclock = eclock.Add(4 * time.Second)
+				e.AskNode(node, Event)
+				e.AskNode(node, Event)
+				stated = stated26
+			} else if got := e.Statements()[node].StatedAt.Format(time.RFC3339); got != stated26 {
+				t.Errorf("the second ask began before the first was taken in: held %s", got)
+			}
+			return json.RawMessage(`{"v":1,"node":"` + node + `","manifest-reads":["a.b"],"stated-at":"` + stated + `"}`), nil
+		}}
+	e.AskNode("ace", Event)
+	held := e.Statements()["ace"]
+	if asks != 2 || held.StatedAt.Format(time.RFC3339) != restated || e.Asking("ace") {
+		t.Errorf("an event during an ask: asked %d times, held stated at %s, asking %v", asks, held.StatedAt, e.Asking("ace"))
+	}
+	if again := strings.Count(strings.Join(lines, "\n"), "asked once more"); again != 1 {
+		t.Errorf("the ask kept for later is said in %d lines, not one: %q", again, lines)
+	}
+	if !held.EventAt.Equal(eclock) || !strings.Contains(string(must(Encode(held))), `"event-at":"2026-11-10T07:36:30Z"`) {
+		t.Errorf("the event's time is not shown: %+v", held)
+	}
 	if Verb != "manifest-reads" || Event != "manifest-reads-changed" || Consumes != "node-engine.manifest-reads-changed" || Invoke != "seat:node-engine.manifest-reads" {
 		t.Errorf("the names are %s %s %s %s", Verb, Event, Consumes, Invoke)
 	}
@@ -167,3 +203,10 @@ func TestReadsCallsSayAnUnansweredNodeHeard(t *testing.T) {
 		t.Errorf("the bound's node is %q %v", n, ok)
 	}
 }
+
+func must(b []byte, err error) []byte {
+	if err != nil {
+		panic(err)
+	}
+	return b
+}