docs: Add v9.4 whats-new for alpha release (#10409)

* docs: Add v9.4 whats-new and changelog for alpha release

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* docs: Add arcgis RenderNode migration to v9.4 whats-new

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Apply suggestions from code review

Co-authored-by: Chris Gervang <chrisgervang@users.noreply.github.com>

* updates

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Ib Green <ib.green.home@gmail.com>

Author: 3 people

docs/whats-new.md

@@ -4,13 +4,42 @@ This page contains highlights of each deck.gl release. Also check our [vis.gl bl
 
 ## deck.gl v9.4
 
-### Views
+Release date: TBD
+
+### Core Performance
+
+- Picking in most instanced layers no longer allocates an `instancePickingColors` attribute buffer, reducing memory usage and initialization times. (deck.gl now using shader builtins `instance_index` / `gl_InstanceID`). 
+
+### Views and Controllers
+
+#### GlobeView
+
+`GlobeView`, while still experimental, is improved and nearing graduation: 
+
+- [TerrainLayer](./api-reference/geo-layers/terrain-layer.md) now renders correctly on `GlobeView`, producing properly projected terrain meshes on the globe.
+- [TerrainExtension](./api-reference/extensions/terrain-extension.md) now supports `GlobeView`, enabling terrain-draped layers on the globe.
+- [Tile3DLayer](./api-reference/geo-layers/tile-3d-layer.md) renders correctly on `GlobeView`.
+
+#### Views
 
 - Views now support a `parameters` prop for per-view GPU draw state overrides. `GlobeView` uses this to enable back-face culling by default, and applications can override it with `new GlobeView({parameters: {cullMode: 'none'}})`.
 
-### Performance
+#### Controllers
+
+- New `doubleClickDragZoom` gesture on all controllers enables smooth zoom by double-clicking and dragging up/down.
+
+### @deck.gl/geo-layers
+
+- [TileLayer](./api-reference/geo-layers/tile-layer.md) now prioritizes tile requests closest to the viewport center, improving perceived load times during panning and zooming.
+- [TerrainLayer](./api-reference/geo-layers/terrain-layer.md) now correctly passes `zoomOffset` through to its child `TileLayer`.
+
+### @deck.gl/arcgis
+
+- `DeckRenderer` now integrates with ArcGIS `SceneView` through the modern `RenderNode` API instead of the deprecated `externalRenderers`.
+
+### @deck.gl/widgets
 
-- Picking in most instanced layers no longer allocates an `instancePickingColors` attribute buffer, instead using shader builtins `instance_index` / `gl_InstanceID`, reducing memory usage and initialization times.
+A new experimental `ViewLayout` system with a helper function `buildViewsFromViewLayout()` allows advanced nested and relative view layouts to be specified using a declarative layout tree.
 
 ## deck.gl v9.3