Implement core diagnostic memory layer, execution helpers, and high-level facade slices

Implemented:
- Core: UTF-16 ReadString boundary/alignment fix, target bitness and process id on MemoryBase
- function interception: PatchManager, DetourManager, InstructionAnalyzer, MainThreadDispatcher
- Execution: BackgroundTaskExecutor, InProcessInvoker
- High-level: Magic facade, RemotePointer, async wrappers
- Discovery/external code loading/Window groundwork (PEB/TEB, pattern scanning, raw allocations, DLL external code loading, window/input)

Tests: 180 passing, 4 integration/interactive tests skipped.

WhiteMagic/Input/InputSimulator.cs

@@ -0,0 +1,73 @@
+using System.Runtime.InteropServices;
+using WhiteMagic.Native;
+
+namespace WhiteMagic.Input;
+
+/// <summary>
+/// Mouse buttons supported by <see cref="InputSimulator.SendMouseClick"/>.
+/// </summary>
+public enum MouseButton
+{
+    /// <summary>The left mouse button.</summary>
+    Left,
+
+    /// <summary>The right mouse button.</summary>
+    Right,
+}
+
+/// <summary>
+/// Simulates keyboard and mouse input directed at a target window via window messages.
+/// </summary>
+public sealed class InputSimulator
+{
+    /// <summary>
+    /// Sends a sequence of character messages to <paramref name="hWnd"/>.
+    /// </summary>
+    /// <returns><see langword="true"/> if every character was posted successfully.</returns>
+    public bool SendKeys(IntPtr hWnd, string text)
+    {
+        if (text is null)
+            throw new ArgumentNullException(nameof(text));
+
+        if (hWnd == IntPtr.Zero)
+            return false;
+
+        foreach (char c in text)
+        {
+            if (!NativeMethods.PostMessageW(hWnd, NativeMethods.WmChar, (nuint)c, 0))
+                return false;
+        }
+
+        return true;
+    }
+
+    /// <summary>
+    /// Sends a mouse click at client-area coordinates <paramref name="x"/>,
+    /// <paramref name="y"/> to <paramref name="hWnd"/>.
+    /// </summary>
+    /// <returns><see langword="true"/> if the click was posted successfully.</returns>
+    public bool SendMouseClick(IntPtr hWnd, int x, int y, MouseButton button)
+    {
+        if (hWnd == IntPtr.Zero)
+            return false;
+
+        nint lParam = MakeLong(x, y);
+
+        (uint down, uint up) = button switch
+        {
+            MouseButton.Left => (NativeMethods.WmLButtonDown, NativeMethods.WmLButtonUp),
+            MouseButton.Right => (NativeMethods.WmRButtonDown, NativeMethods.WmRButtonUp),
+            _ => throw new ArgumentOutOfRangeException(nameof(button)),
+        };
+
+        if (!NativeMethods.PostMessageW(hWnd, down, 0, lParam))
+            return false;
+
+        return NativeMethods.PostMessageW(hWnd, up, 0, lParam);
+    }
+
+    private static nint MakeLong(int low, int high)
+    {
+        return (nint)((uint)low | ((uint)high << 16));
+    }
+}