Fix: Blazor render crash on session delete

Session deletion triggered rapid render batch churn:
1. Session.DisposeAsync() talked to CLI, triggering SDK events
2. OnStateChanged fired from CloseSessionAsync
3. ReconcileOrganization fired another OnStateChanged

This caused Blazor render batch ordering races ('r.parentNode.removeChild'
on null) and 'unexpected acknowledgement for render batch N' errors.

Fix: move DisposeAsync to fire-and-forget after UI update, and remove
redundant ReconcileOrganization call (session already removed from
_sessions, reconciliation just caused extra state churn).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: PureWeen

PolyPilot/Services/CopilotService.cs

@@ -2411,9 +2411,6 @@ internal async Task<bool> CloseSessionCoreAsync(string name, bool notifyUi)
         // Track session close using display name (consistent with TrackSessionStart key)
         _usageStats?.TrackSessionEnd(name);
 
-        if (state.Session is not null)
-            try { await state.Session.DisposeAsync(); } catch { /* session may already be disposed */ }
-
         // Clean up auto-created temp directory for empty sessions
         if (state.Info.WorkingDirectory != null)
         {
@@ -2433,12 +2430,26 @@ internal async Task<bool> CloseSessionCoreAsync(string name, bool notifyUi)
             _activeSessionName = _sessions.Keys.FirstOrDefault();
         }
 
+        // Single state change notification — ReconcileOrganization is unnecessary here
+        // because the session was already removed from _sessions above. Calling it would
+        // trigger a second OnStateChanged, causing rapid render batch churn that crashes
+        // Blazor with "r.parentNode.removeChild" on null (render batch ordering race).
         if (notifyUi)
             OnStateChanged?.Invoke();
         if (!IsRemoteMode)
-        {
             SaveActiveSessionsToDisk();
-            ReconcileOrganization();
+
+        // Dispose the SDK session AFTER UI has updated — DisposeAsync talks to the CLI
+        // process and may trigger additional SDK events on background threads. Running it
+        // after the state change prevents render batch collisions.
+        if (state.Session is not null)
+        {
+            var session = state.Session;
+            _ = Task.Run(async () =>
+            {
+                try { await session.DisposeAsync(); }
+                catch { /* session may already be disposed */ }
+            });
         }
         return true;
     }