Session Sync Repair

Nucleic-Session: 0C7BC346-0002-4533-ADDD-3B4C92E58527
Co-authored-by: Nucleic <[email protected]>

NucleicRemote/NucleicRemote/Models/HostConnection.swift

@@ -35,7 +35,20 @@ final class HostConnection {
 
     /// The session RemoteStore currently has open on this host, if any — so snapshot/events are only
     /// forwarded (and deduped) for the transcript on screen. Set by RemoteStore on open/close.
-    var openSessionID: SessionID?
+    /// Changing which session is open resets the per-session cursor + dedup set (they only make
+    /// sense within one transcript).
+    var openSessionID: SessionID? {
+        didSet {
+            guard openSessionID != oldValue else { return }
+            openMaxSeq = nil
+            seenSeq = []
+        }
+    }
+
+    /// The highest event `seq` delivered for the open session — the warm-resubscribe cursor. On a
+    /// reconnect we re-subscribe `sinceSeq: openMaxSeq` so the host replays only what we missed
+    /// instead of cold-resetting to the 200-event tail (which would truncate a long transcript).
+    private var openMaxSeq: UInt64?
 
     // MARK: Callbacks up to RemoteStore (aggregate concerns)