Merge branch 'codex/jetstream-full-parity-executeplan' into main

# Conflicts:
#	differences.md
#	docs/plans/2026-02-23-jetstream-full-parity-plan.md
#	src/NATS.Server/Auth/Account.cs
#	src/NATS.Server/Configuration/ConfigProcessor.cs
#	src/NATS.Server/Monitoring/VarzHandler.cs
#	src/NATS.Server/NatsClient.cs
#	src/NATS.Server/NatsOptions.cs
#	src/NATS.Server/NatsServer.cs

src/NATS.Server/Subscriptions/RemoteSubscription.cs

@@ -0,0 +1,3 @@
+namespace NATS.Server.Subscriptions;
+
+public sealed record RemoteSubscription(string Subject, string? Queue, string RouteId);

src/NATS.Server/Subscriptions/SubList.cs

@@ -13,6 +13,7 @@ public sealed class SubList : IDisposable
 
     private readonly ReaderWriterLockSlim _lock = new();
     private readonly TrieLevel _root = new();
+    private readonly Dictionary<string, RemoteSubscription> _remoteSubs = new(StringComparer.Ordinal);
     private Dictionary<string, CachedResult>? _cache = new(StringComparer.Ordinal);
     private uint _count;
     private volatile bool _disposed;
@@ -96,6 +97,40 @@ public sealed class SubList : IDisposable
         }
     }
 
+    public void ApplyRemoteSub(RemoteSubscription sub)
+    {
+        _lock.EnterWriteLock();
+        try
+        {
+            var key = $"{sub.RouteId}|{sub.Subject}|{sub.Queue}";
+            _remoteSubs[key] = sub;
+            Interlocked.Increment(ref _generation);
+        }
+        finally
+        {
+            _lock.ExitWriteLock();
+        }
+    }
+
+    public bool HasRemoteInterest(string subject)
+    {
+        _lock.EnterReadLock();
+        try
+        {
+            foreach (var remoteSub in _remoteSubs.Values)
+            {
+                if (SubjectMatch.MatchLiteral(subject, remoteSub.Subject))
+                    return true;
+            }
+
+            return false;
+        }
+        finally
+        {
+            _lock.ExitReadLock();
+        }
+    }
+
     public void Insert(Subscription sub)
     {
         var subject = sub.Subject;