A Dante device Companion's module never listed before gets the Dante Controller connection restarted once

The module only reads a device's channels when it starts, so a receiver added later is missing
from the crosspoint lists until the connection restarts (the two AD4Q receivers today). The
watchdog now remembers every Dante device it has seen in state.json and, when a newcomer appears,
restarts that connection once: never during a live service, at most every ten minutes, and never
for a device that merely dropped out and came back.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/test_status_panel.py

@@ -2255,3 +2255,52 @@ class TestCoreMIDI(unittest.TestCase):
 
 if __name__ == "__main__":
     unittest.main()
+
+
+class TestDanteNewcomers(unittest.TestCase):
+    """A Dante device the module never listed before gets the Dante Controller connection restarted once."""
+
+    def setUp(self):
+        self.snap = healthy_snapshot(time.time())
+        self.engine = sp.Engine(CONFIG, None)
+        self.restarts = []
+        me = self
+
+        class Comp:
+            def restart_connection(self, cid):
+                me.restarts.append(cid); return True
+        self.comp = Comp()
+        self.label = sp.dante_label(CONFIG)
+        self.snap.conns[self.label] = {"id": "dante-1", "enabled": True, "category": "good"}
+
+    def devices(self, names):
+        self.snap.vars[(self.label, "devices")] = json.dumps(names)
+
+    def test_first_list_is_remembered_then_a_newcomer_restarts_once(self):
+        now = time.time()
+        self.devices(["A", "B"])
+        self.assertFalse(sp.watch_dante_newcomers(self.snap, CONFIG, self.comp, self.engine, now))
+        self.assertEqual(self.engine.state.get("dante_known"), ["A", "B"])
+        self.assertFalse(sp.watch_dante_newcomers(self.snap, CONFIG, self.comp, self.engine, now + 60))    # nothing new
+        self.devices(["A", "B", "BOH-AD4Q-A"])
+        self.assertTrue(sp.watch_dante_newcomers(self.snap, CONFIG, self.comp, self.engine, now + 120))
+        self.assertEqual(self.restarts, ["dante-1"])
+        self.assertEqual(self.engine.state.get("dante_known"), ["A", "B", "BOH-AD4Q-A"])
+        self.devices(["A", "B", "BOH-AD4Q-A", "X"])
+        self.assertFalse(sp.watch_dante_newcomers(self.snap, CONFIG, self.comp, self.engine, now + 180))   # ten-minute cooldown
+        self.assertTrue(sp.watch_dante_newcomers(self.snap, CONFIG, self.comp, self.engine, now + 800))
+        self.assertEqual(len(self.restarts), 2)
+        self.devices(["A", "B"])                                                                            # devices going away never restart
+        self.assertFalse(sp.watch_dante_newcomers(self.snap, CONFIG, self.comp, self.engine, now + 2000))
+        self.devices(["A", "B", "BOH-AD4Q-A"])                                                              # nor coming back
+        self.assertFalse(sp.watch_dante_newcomers(self.snap, CONFIG, self.comp, self.engine, now + 2600))
+
+    def test_waits_for_the_service_to_end(self):
+        now = time.time()
+        self.devices(["A"])
+        sp.watch_dante_newcomers(self.snap, CONFIG, self.comp, self.engine, now)
+        self.devices(["A", "NEW"])
+        self.engine.any_recording = True
+        self.assertFalse(sp.watch_dante_newcomers(self.snap, CONFIG, self.comp, self.engine, now + 100))
+        self.engine.any_recording = False
+        self.assertTrue(sp.watch_dante_newcomers(self.snap, CONFIG, self.comp, self.engine, now + 200))