chore: add changelog fragment and what's-new entry for DS dual-screen (#3509)

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

Author: github-actions[bot]

.changelog/3509.md

@@ -0,0 +1,5 @@
+### Added
+- **DS Dual-Screen Metal Rendering** — Nintendo DS games with a DeltaSkin active now render both screens as GPU-side sub-rectangle blits in a single Metal render pass. The combined 256×384 DS framebuffer is split into top (rows 0–191) and bottom (rows 192–383) viewports that match the skin's screen layout, supporting portrait (stacked) and landscape (side-by-side) configurations.
+
+### Changed
+- **melonDS / DeSmuME skin support** — `supportsSkins` is now `true` for both DS cores, enabling DeltaSkin overlays and controller layouts when a compatible skin is installed.

PVUI/Sources/PVSwiftUI/Resources/whats-new.json

@@ -568,5 +568,23 @@
         "subtitle": "Drop an unzipped DOSBox game folder into the Imports directory. Any folder with .exe, .com, .bat, or .conf files is recognised automatically as a DOS game."
       }
     ]
+  },
+  {
+    "version": "3.8.0",
+    "title": "DS Dual-Screen Skins",
+    "features": [
+      {
+        "symbolName": "rectangle.split.1x2.fill",
+        "symbolColor": "blue",
+        "title": "Nintendo DS Dual-Screen Skins",
+        "subtitle": "DS games now support full DeltaSkin overlays with GPU-accelerated dual-screen rendering. Both top and bottom screens are positioned independently according to your skin layout."
+      },
+      {
+        "symbolName": "square.3.layers.3d",
+        "symbolColor": "purple",
+        "title": "Metal Sub-Rectangle Rendering",
+        "subtitle": "The DS framebuffer is split into two sub-rectangles on the GPU in a single render pass — no extra copies, minimal overhead."
+      }
+    ]
   }
 ]