fix: an event's teardown removes a boss's adds (D287)

The walk found an event run's boss adds outliving the run: teardown
removes what a step placed by net id, and the adds RunicNPC spawned for
a boss's phase are in no step's ledger. RunicNPC now keeps each boss's
live adds by the boss's net id, after the boss dies too, and
RunicNpc_Despawn(<boss net id>) removes them with it, which is the call
the bridge's teardown makes. An add leaves the set when it dies.

Walked on the Oxide rig: event 36, run 65 placed the boss, its phase
summoned two adds owned by run:65, the boss was killed, the event
advanced on rust.boss.killed, and the run's cleanup removed both adds.
New harness check s6.boss.despawnTakesAdds.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

plugin/RunicNPC.cs

@@ -3212,6 +3212,10 @@ namespace Oxide.Plugins
             Index(npc, false);
             if (npc.IsBoss)
                 ClearBar(npc);
+            if (_addsOf.Count > 0)
+                foreach (ulong boss in _addsOf.Keys.ToList())
+                    if (_addsOf[boss].Remove(npc) && _addsOf[boss].Count == 0)
+                        _addsOf.Remove(boss);
 
             if (npc.PlacementId != null)
             {
@@ -3542,6 +3546,12 @@ namespace Oxide.Plugins
         /// <summary>The bosses alive now.</summary>
         private readonly HashSet<RunicNpcPlayer> _bosses = new HashSet<RunicNpcPlayer>();
 
+        /// <summary>
+        ///     Each boss's live adds, by the boss's net id, kept after the boss dies (D287) so that despawning
+        ///     the boss's id removes them too. An add leaves its set when it dies or despawns.
+        /// </summary>
+        private readonly Dictionary<ulong, HashSet<RunicNpcPlayer>> _addsOf = new Dictionary<ulong, HashSet<RunicNpcPlayer>>();
+
         /// <summary>Whose bar each player sees, by Steam id: one boss at a time, the nearest that qualifies (D274).</summary>
         private readonly Dictionary<ulong, RunicNpcPlayer> _barShown = new Dictionary<ulong, RunicNpcPlayer>();
 
@@ -3692,6 +3702,7 @@ namespace Oxide.Plugins
 
             Vector3 centre = boss.transform.position;
             string owner = boss.Owner;
+            ulong bossId = boss.NetId;
             var attackers = boss.Contributors.Keys.ToList();
             float turn = UnityEngine.Random.value * Mathf.PI * 2f;
             int i = 0;
@@ -3712,12 +3723,18 @@ namespace Oxide.Plugins
                 if (add == null)
                     PrintWarning($"{boss.RnName} ({boss.ProfileName}): add {i + 1} of {adds.Count} ('{adds.Profile}') not placed: {error}");
                 else
+                {
+                    HashSet<RunicNpcPlayer> mine;
+                    if (!_addsOf.TryGetValue(bossId, out mine))
+                        _addsOf[bossId] = mine = new HashSet<RunicNpcPlayer>();
+                    mine.Add(add);
                     foreach (ulong id in attackers)
                     {
                         BasePlayer who = BasePlayer.FindByID(id);
                         if (who != null && who.IsAlive() && Vector3.Distance(who.transform.position, add.transform.position) <= 100f)
                             Learn(add, who, true);
                     }
+                }
 
                 i++;
                 if (i < adds.Count)
@@ -4251,10 +4268,25 @@ namespace Oxide.Plugins
             return npc;
         }
 
+        /// <summary>
+        ///     Removes one NPC, and for a boss the adds it summoned, alive or not (D287): an event's teardown
+        ///     removes what its step placed by net id, and a boss's adds are in no step's ledger. The boss may
+        ///     already be dead; its adds are still found by its net id.
+        /// </summary>
         private int RunicNpc_Despawn(ulong netId)
         {
+            var gone = new List<RunicNpcPlayer>();
             RunicNpcPlayer npc;
-            return _npcs.TryGetValue(netId, out npc) ? Despawn(new[] { npc }) : 0;
+            if (_npcs.TryGetValue(netId, out npc))
+                gone.Add(npc);
+            HashSet<RunicNpcPlayer> adds;
+            if (_addsOf.TryGetValue(netId, out adds))
+            {
+                gone.AddRange(adds);
+                _addsOf.Remove(netId);
+            }
+
+            return Despawn(gone);
         }
 
         private int RunicNpc_DespawnOwner(string owner) => owner == null ? 0 : Despawn(_npcs.Values.Where(n => n.Owner == owner));