review: clear stale attribution, gate numberless PUTs, cite the ADR

A Poll finding a higher number now clears series.latest_raised_by: the value
it stores is its own, so the next Poll must not credit that Reader with an
agreement they did not earn, nor charge them for a retraction of a number
they never reported.

A PUT carrying no chapter is no Sighting and defers nothing. The ceiling now
counts the Site's own rest rather than defaultRest. The userscripts PUT an
unchanged read too - the case the whole mechanism exists for was the one they
never sent.

ADR-0011 carries its citations and states honestly when a Reader's marks take
effect.

backend/internal/latest/sighting_test.go

@@ -189,7 +189,7 @@ func TestSightingCeilingForcesPoll(t *testing.T) {
 	newTestPoller(t, s, f, now).runOnce(context.Background())
 
 	if got := f.callCount(); got != 1 {
-		t.Fatalf("fetched %d times past the %s ceiling, want 1", got, sightingCeiling)
+		t.Fatalf("fetched %d times past the %s ceiling, want 1", got, sightingCeilingRests*defaultRest)
 	}
 }
 
@@ -439,3 +439,56 @@ func TestPollFindingHigherNumberIsNotAContradiction(t *testing.T) {
 		t.Fatalf("a Reader whose report the Site overtook lost the right to defer (fetches %d, want 1)", got)
 	}
 }
+
+// A Poll that overtakes a Sighting takes ownership of the row: the value stored
+// afterwards is the Poll's own, so a later retraction is not the Reader's fault
+// and must not be charged to them.
+func TestAttributionDoesNotSurviveAPollThatOvertookIt(t *testing.T) {
+	s, _ := newTestStore(t)
+	now := time.UnixMilli(20 * time.Hour.Milliseconds())
+	seedDemonic(t, s, now.Add(-2*time.Hour).UnixMilli())
+	sight(t, s, s.OwnerID(), demonicKey, 295, now.Add(-10*time.Minute))
+
+	f := &fakeFetcher{body: demonicFixture(296), status: 200}
+	p := newTestPoller(t, s, f, now)
+	at := now.Add(defaultRest + time.Minute)
+	p.Now = func() time.Time { return at }
+	p.runOnce(context.Background())
+	if got := readLatestNum(t, s, s.OwnerID(), demonicKey); got != 296 {
+		t.Fatalf("latest after the Poll = %v, want the Site's own 296", got)
+	}
+
+	var logs strings.Builder
+	prev := log.Writer()
+	log.SetOutput(&logs)
+	t.Cleanup(func() { log.SetOutput(prev) })
+
+	f.body = demonicFixture(290) // the Site retracts what only the Poll wrote
+	p.Now = func() time.Time { return at.Add(defaultRest + time.Minute) }
+	p.runOnce(context.Background())
+	if strings.Contains(logs.String(), "sighting contradicted") {
+		t.Fatalf("a retraction of the Poll's own value was charged to a Reader: %s", logs.String())
+	}
+}
+
+// A PUT with no Latest Chapter in it — a favourite toggle, progress written
+// from a chapter page — is nobody looking at the Series page, so it buys no
+// deferral. Otherwise a client could suppress a Series' Polls while reporting
+// nothing, and with nothing reported there would be nothing to judge.
+func TestPutWithoutALatestChapterDoesNotDefer(t *testing.T) {
+	s, _ := newTestStore(t)
+	now := time.UnixMilli(20 * time.Hour.Milliseconds())
+	seedDemonic(t, s, now.Add(-2*time.Hour).UnixMilli())
+	// The handler's own call, with the field the client omitted.
+	if err := s.RecordSighting(s.OwnerID(), "demonic", "Catastrophic-Necromancer",
+		nil, now.Add(-time.Minute).UnixMilli()); err != nil {
+		t.Fatalf("RecordSighting: %v", err)
+	}
+
+	f := &fakeFetcher{body: demonicFixture(296), status: 200}
+	p := newTestPoller(t, s, f, now)
+	p.runOnce(context.Background())
+	if got := f.callCount(); got != 1 {
+		t.Fatalf("fetched %d times after a PUT carrying no chapter, want 1", got)
+	}
+}