Add Z80 CPU skeleton, RegisterPair struct, and MemoryBus implementation

Core/Memory/MemoryBus.cs

@@ -0,0 +1,47 @@
+using System;
+using Core.Interfaces;
+
+namespace Core.Memory
+{
+    public class MemoryBus : IMemory
+    {
+        // The flat 64KB memory space
+        private readonly byte[] _memory = new byte[0x10000];
+
+        public byte Read(ushort address)
+        {
+            return _memory[address];
+        }
+
+        public void Write(ushort address, byte value)
+        {
+            /* ZX Spectrum 48K Memory Map:
+             * 0x0000 - 0x3FFF: ROM (16KB) -> Cannot write here!
+             * 0x4000 - 0x57FF: Display File (Screen Pixels)
+             * 0x5800 - 0x5AFF: Color Attributes
+             * 0x5B00 - 0xFFFF: General Purpose RAM
+             */
+
+            if (address < 0x4000)
+            {
+                // Attempted to write to the ROM area. 
+                // We simply ignore the write command, just like real hardware.
+                return;
+            }
+
+            _memory[address] = value;
+        }
+
+        // Helper method to load the original Sinclair ROM file
+        public void LoadRom(byte[] romData)
+        {
+            if (romData.Length > 0x4000)
+            {
+                throw new ArgumentException("ROM file exceeds the 16KB capacity of Bank 0.");
+            }
+
+            // Copy the ROM data into the very beginning of the memory array
+            Array.Copy(romData, 0, _memory, 0, romData.Length);
+        }
+    }
+}