fix(hands): watchdog seen moves only on a new peer beat, tracked by message id

tests/test_heartbeat.py

@@ -1,3 +1,4 @@
+import json
 import logging
 from datetime import UTC, datetime, timedelta
 from types import SimpleNamespace
@@ -113,6 +114,59 @@ def test_fresh_beat_arms_and_stays_quiet(tmp_path):
     assert w.seen == NOW and w.top == 100
 
 
+def test_same_beat_seen_twice_does_not_move_seen(tmp_path):
+    w = state(tmp_path)
+    old = hb(NOW - timedelta(hours=1), eid=200)
+    first = look(w, [old], now=NOW, res=None, full=True)
+    assert first.armed and first.alarm is None
+    assert w.seen == NOW and w.beat_id == 200
+
+    # Тот же самый hb в окне следующего прогона - это не новое показание
+    again = look(w, [old], now=NOW + timedelta(hours=6), res=None, full=True)
+    assert w.seen == NOW and again.alarm is None
+    assert "отметка та же" in again.note
+
+    # И через порог 36h та же отметка уже не выглядит живой цепью
+    late = NOW + timedelta(hours=37)
+    loud = look(w, [old], now=late, res=None, full=True)
+    assert loud.alarm == "silence" and w.seen == NOW
+    assert loud.age is not None and loud.age > timedelta(hours=36)
+
+    # Пришла новая отметка - новый id, и seen снова двигается
+    fresh = look(w, [old, hb(late, eid=201)], now=late, res=None, full=True)
+    assert fresh.alarm is None and w.seen == late and w.beat_id == 201
+
+
+def test_state_without_beat_id_trusts_its_own_seen(tmp_path):
+    path = tmp_path / "сторож.json"
+    path.write_text(
+        json.dumps(
+            {
+                "version": 1,
+                "at": "2026-09-21T05:00:01Z",
+                "seen": "2026-09-22T05:42:01Z",
+                "every": 86400,
+                "every_unknown": False,
+                "top": 300,
+                "alerted": None,
+                "unarmed_since": None,
+                "unarmed_told": False,
+            }
+        ),
+        encoding="utf-8",
+    )
+    w = Watch.load(path)
+    was = datetime(2026, 9, 22, 5, 42, 1, tzinfo=UTC)
+    assert w.beat_id == 0 and w.seen == was
+
+    old = hb(datetime(2026, 9, 21, 5, 0, 1, tzinfo=UTC), eid=305)
+    assert look(w, [old], now=NOW, res=None, full=True).alarm is None
+    assert w.seen == was and w.beat_id == 305
+    # Старое состояние не пере-вооружилось на старой отметке: порог придёт в срок
+    over = datetime(2026, 9, 23, 20, 0, tzinfo=UTC)
+    assert look(w, [old], now=over, res=None, full=True).alarm == "silence"
+
+
 def test_threshold_is_every_times_one_and_a_half(tmp_path):
     # 30 часов при every=24h - ещё не тревога: одна потерянная строка не в счёт
     quiet = state(tmp_path, seen=NOW - timedelta(hours=30), every=timedelta(hours=24))
@@ -265,6 +319,7 @@ def test_state_survives_a_round_trip(tmp_path):
         seen=NOW,
         every=timedelta(hours=24),
         every_unknown=True,
+        beat_id=329,
         top=42,
         alerted=NOW,
         unarmed_since=None,
@@ -273,6 +328,7 @@ def test_state_survives_a_round_trip(tmp_path):
     w.save()
     back = Watch.load(w.path)
     assert back.at == NOW and back.seen == NOW and back.top == 42
+    assert back.beat_id == 329
     assert back.every == timedelta(hours=24) and back.every_unknown
     assert back.alerted == NOW and back.unarmed_told
     assert Watch.load(tmp_path / "нет.json").seen is None