fix(centralui): DialogHost cleanup only on open->closed transition + drop trailing class space (T33a review)

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Shared/DialogHost.razor

@@ -17,7 +17,7 @@
          role="dialog"
          aria-modal="true"
          @onkeydown="OnKeyDown">
-        <div class="modal-dialog modal-dialog-centered @state.Size" role="document">
+        <div class="modal-dialog modal-dialog-centered@(state.Size is null ? "" : $" {state.Size}")" role="document">
             <div class="modal-content">
                 <div class="modal-header">
                     <h5 class="modal-title">@state.Title</h5>
@@ -125,14 +125,20 @@
         }
         else
         {
-            _focusedForState = null;
-            try { await JS.InvokeVoidAsync("document.body.classList.remove", "modal-open"); }
-            catch { /* prerender: no JS — ignore */ }
+            // Only clean up on the actual open→closed transition. Skipping when
+            // _focusedForState is already null avoids spurious JS interop on
+            // the initial render and every steady-state no-dialog render.
+            if (_focusedForState is not null)
+            {
+                _focusedForState = null;
+                try { await JS.InvokeVoidAsync("document.body.classList.remove", "modal-open"); }
+                catch { /* prerender: no JS — ignore */ }
 
-            // Return focus to whatever element triggered the dialog so keyboard
-            // users are not dumped at the top of the document on close.
-            try { await JS.InvokeVoidAsync("sbDialog.restoreActiveElement"); }
-            catch { /* prerender: no JS — ignore */ }
+                // Return focus to whatever element triggered the dialog so keyboard
+                // users are not dumped at the top of the document on close.
+                try { await JS.InvokeVoidAsync("sbDialog.restoreActiveElement"); }
+                catch { /* prerender: no JS — ignore */ }
+            }
         }
     }