feat(ds): enable skin support for melonDS, desmume2015, and ThinLibretroCore DS

- Set supportsSkins = true on PVMelonDSCore and PVDesmume2015Core
- Remove com.provenance.ds from PVThinLibretroCore skinUnsupportedSystems
- Add supportsDualScreens = true for DS system in PVThinLibretroCore
- DefaultDeltaSkin NDS dual-screen portrait/landscape layouts already present

Part of #2540

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

Author: github-actions[bot]

.changelog/3377.md

@@ -0,0 +1,2 @@
+### Added
+- **DS Dual-Screen Skin Support (Phase 1)** — Enable Delta skin support for melonDS, desmume2015, and PVThinLibretroCore DS system; NDS dual-screen portrait/landscape layouts were already present in DefaultDeltaSkin and are now active.

Cores/Desmume2015/PVDesmume2015Core/Core/PVDesmume2015Core.swift

@@ -15,8 +15,7 @@ import PVCoreBridgeRetro
 @objc
 @objcMembers
 open class PVDesmume2015Core: PVEmulatorCore {
-    /// Dual-screen skin layouts are not yet supported; disable until implemented.
-    public override var supportsSkins: Bool { false }
+    public override var supportsSkins: Bool { true }
 
     public override var supportsDualScreens: Bool { true }
 

Cores/melonDS/PVMelonDSCore/Core/PVMelonDSCore.swift

@@ -15,8 +15,7 @@ import PVCoreBridgeRetro
 @objc
 @objcMembers
 public final class PVMelonDSCore: PVEmulatorCore {
-    /// Dual-screen skin layouts are not yet supported; disable until implemented.
-    public override var supportsSkins: Bool { false }
+    public override var supportsSkins: Bool { true }
 
     public override var supportsDualScreens: Bool { true }
 

PVCoreBridgeRetro/Sources/PVLibRetro/PVThinLibretroCore.swift

@@ -66,9 +66,10 @@ class PVThinLibretroCore: PVEmulatorCore {
 
     /// Systems that don't have adequate skin support — disable skins to show
     /// the native on-screen controls or core-specific overlays instead.
+    /// NOTE: "com.provenance.ds" is intentionally NOT listed here — DS skins
+    /// use the DefaultDeltaSkin NDS dual-screen layout (portrait + landscape).
     private static let skinUnsupportedSystems: Set<String> = [
         "com.provenance.3ds",
-        "com.provenance.ds",
         "com.provenance.dos",
         "com.provenance.mame",
         "com.provenance.arcade",
@@ -85,6 +86,12 @@ class PVThinLibretroCore: PVEmulatorCore {
         return !Self.skinUnsupportedSystems.contains(sysId)
     }
 
+    /// DS (NDS) cores output a combined 256×384 framebuffer (top screen + bottom screen).
+    /// The DefaultDeltaSkin NDS layout splits this into two independently positioned viewports.
+    public override var supportsDualScreens: Bool {
+        systemIdentifier == "com.provenance.ds"
+    }
+
     required init() {
         super.init()
         self.bridge = (_bridge as! any ObjCBridgedCoreBridge)