Add PS_Editor plugin Phase 1: GameMode + Camera navigation

Runtime editor plugin with UE viewport-style camera controls:
- ZQSD/Arrows movement (always active), E/A for up/down
- LMB: pan (horizontal move + yaw), RMB: free fly look
- Alt+LMB / MMB: orbit around focal point, scroll: zoom
- HUD with controls help, cursor auto-hide during camera ops

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Unreal/Plugins/PS_Editor/Binaries/Win64/UnrealEditor.modules

@@ -0,0 +1,7 @@
+{
+	"BuildId": "37670630",
+	"Modules": 
+	{
+		"PS_Editor": "UnrealEditor-PS_Editor.dll"
+	}
+}