fix(adminui): close a browse session that opens after its picker is gone (R04 L4)

Every picker and RawBrowseModal stored the OpenAsync token after the await; if
the host was disposed (or the modal closed) meanwhile, its teardown had already
run with no token, so the plant-side session lived until the reaper's idle TTL.
BrowseOpenGuard.CloseIfOrphaned closes it at once; each host sets _disposed
first thing in DisposeAsync (RawBrowseModal also treats !Visible as gone).

Refs #745
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/Pickers/SqlAddressPickerBody.razor

@@ -240,6 +240,8 @@ else
     private string _built = "";
     private string _selectedColumnNodeId = "";
     private Guid _token = Guid.Empty;
+    // Set first thing in DisposeAsync; an open that lands afterwards closes its own session.
+    private volatile bool _disposed;
     private bool _opening;
     private bool _canOperate;
     private string? _openError;
@@ -268,6 +270,8 @@ else
             // sole place it is read, and it dies with the local variable.
             var json = BuildBrowseConfig();
             var result = await BrowserService.OpenAsync(DriverTypeNames.Sql, json, default);
+            // Host disposed mid-open: close the session nobody will (R04 L4).
+            if (BrowseOpenGuard.CloseIfOrphaned(result, _disposed, BrowserService)) { return; }
             if (result.Ok) { _token = result.Token; }
             else { _openError = result.Message; }
         }
@@ -429,6 +433,7 @@ else
 
     public ValueTask DisposeAsync()
     {
+        _disposed = true;
         if (_token != Guid.Empty)
         {
             // Fire-and-forget — don't block circuit teardown on a slow database.