fix(parallax): animate background-position-y directly so SSR parallax works pre-WASM

DeepDrftShared.Client/Components/ParallaxImage.razor.cs

@@ -87,11 +87,11 @@ public abstract class ParallaxImageBase : ComponentBase, IAsyncDisposable
     private string? _handle;
 
     // --parallax-from/--parallax-to are inherited custom properties read by the
-    // CSS @keyframes parallax-pan (scroll-driven animation on .parallax-window).
-    // They encode ParallaxSpeed and InvertDirection. --parallax-pos itself is
-    // never set inline — an inline value would beat the CSS animation in the
-    // cascade and defeat the pre-WASM scroll-driven parallax. JS sets it inline
-    // only after WASM boots, transparently taking over (inline > animation).
+    // CSS @keyframes parallax-pan, which animates background-position-y on each
+    // .layer (scroll-driven, pre-WASM). They encode ParallaxSpeed and
+    // InvertDirection. After WASM boots, parallax.js sets data-parallax-active to
+    // cancel that animation and drives background-position-y on the layers
+    // directly — a clean handoff with no competing writers.
     private string ParallaxVars()
     {
         var end = (int)Math.Round(ParallaxSpeed * 100);