Fix InputSimulator wParam, PeHeaderParser double-parse, and other review issues

Bug fixes:
- InputSimulator: Pass correct button state (MK_LBUTTON/MK_RBUTTON) in wParam for button-down messages instead of 0.
- PeHeaderParser: ParseOptionalHeader now reads only the optional header, not section headers (fixes double-parse waste).
- EntryPoint: Removed useless isPe32Plus branch (AddressOfEntryPoint is at offset 16 in both PE32 and PE32+).
- RemoteWindow: Handle null foreground window case in Activate to avoid calling GetWindowThreadProcessId with HWND 0.
- RemotePointer: Remove dead null-conditional operators (encoding ??) since encoding is non-nullable.

Constants added:
- SystemMethods: MkLButton (0x0001) and MkRButton (0x0002) for mouse button state flags.

Tests: 199 passing, 4 integration/interactive skipped.

WhiteMagic/Input/InputSimulator.cs

@@ -53,16 +53,17 @@ public sealed class InputSimulator
 
         nint lParam = MakeLong(x, y);
 
-        (uint down, uint up) = button switch
+        (uint down, uint downWParam) = button switch
         {
-            MouseButton.Left => (NativeMethods.WmLButtonDown, NativeMethods.WmLButtonUp),
-            MouseButton.Right => (NativeMethods.WmRButtonDown, NativeMethods.WmRButtonUp),
+            MouseButton.Left => (NativeMethods.WmLButtonDown, NativeMethods.MkLButton),
+            MouseButton.Right => (NativeMethods.WmRButtonDown, NativeMethods.MkRButton),
             _ => throw new ArgumentOutOfRangeException(nameof(button)),
         };
 
-        if (!NativeMethods.PostMessageW(hWnd, down, 0, lParam))
+        if (!NativeMethods.PostMessageW(hWnd, down, downWParam, lParam))
             return false;
 
+        uint up = button == MouseButton.Left ? NativeMethods.WmLButtonUp : NativeMethods.WmRButtonUp;
         return NativeMethods.PostMessageW(hWnd, up, 0, lParam);
     }