Phase 0 completion: NT8 SDK core framework with risk management and position sizing

src/NT8.Adapters/PlaceholderAdapter.cs

@@ -0,0 +1,16 @@
+// Placeholder file for NT8.Adapters project
+// This will contain NinjaTrader 8 integration adapters in Phase 1
+
+using System;
+
+namespace NT8.Adapters
+{
+    /// <summary>
+    /// Placeholder class to make project compile
+    /// Will be removed when actual NT8 adapters are implemented
+    /// </summary>
+    internal class PlaceholderAdapter
+    {
+        // Intentionally empty - just for compilation
+    }
+}