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/Discovery/PeHeaderParser.cs

@@ -64,21 +64,8 @@ public sealed class PeHeaderParser
             if (optionalHeader is null)
                 return IntPtr.Zero;
 
-            // Entry point is at different offsets for PE32 vs PE32+
-            bool isPe32Plus = IsPe32Plus();
-
-            if (isPe32Plus)
-            {
-                // PE32+: AddressOfEntryPoint is at offset 16 in OPTIONAL_HEADER (64-bit)
-                return (IntPtr)BitConverter.ToUInt32(
-                    optionalHeader.AsSpan(16, 4));
-            }
-            else
-            {
-                // PE32: AddressOfEntryPoint is at offset 16 in OPTIONAL_HEADER (32-bit)
-                return (IntPtr)BitConverter.ToUInt32(
-                    optionalHeader.AsSpan(16, 4));
-            }
+            // Entry point RVA is at offset 16 in the optional header (both PE32 and PE32+)
+            return (IntPtr)BitConverter.ToUInt32(optionalHeader.AsSpan(16, 4));
         }
     }
 
@@ -185,7 +172,46 @@ public sealed class PeHeaderParser
     /// </summary>
     private (byte[]? OptionalHeader, byte[][]? SectionHeaders) ParseOptionalHeader()
     {
-        return ParseOptionalHeaderAndSectionHeaders();
+        // Read DOS header (first 64 bytes)
+        byte[] dosHeader = _memory.ReadBytes(_baseAddress, 64);
+        if (dosHeader.Length < 64)
+            throw new InvalidDataException("Failed to read DOS header.");
+
+        // Verify DOS signature "MZ"
+        if (dosHeader[0] != 0x4D || dosHeader[1] != 0x5A)
+            throw new InvalidDataException("Invalid DOS signature (not a PE file).");
+
+        // PE header offset is at 0x3C in DOS header
+        int peOffset = BitConverter.ToInt32(dosHeader, 0x3C);
+        if (peOffset < 0 || peOffset > 0x1000) // Sanity check
+            throw new InvalidDataException($"Invalid PE offset: {peOffset}");
+
+        // Read PE signature (4 bytes: "PE\0\0")
+        IntPtr peSigAddr = _baseAddress + peOffset;
+        byte[] peSignature = _memory.ReadBytes(peSigAddr, 4);
+        if (peSignature.Length < 4)
+            throw new InvalidDataException("Failed to read PE signature.");
+
+        if (peSignature[0] != 0x50 || peSignature[1] != 0x45 ||
+            peSignature[2] != 0x00 || peSignature[3] != 0x00)
+            throw new InvalidDataException("Invalid PE signature.");
+
+        // COFF header follows PE signature (20 bytes)
+        IntPtr coffAddr = peSigAddr + 4;
+        byte[] coffHeader = _memory.ReadBytes(coffAddr, 20);
+        if (coffHeader.Length < 20)
+            throw new InvalidDataException("Failed to read COFF header.");
+
+        // SizeOfOptionalHeader is at offset 16 in COFF header
+        ushort sizeOfOptionalHeader = BitConverter.ToUInt16(coffHeader, 16);
+
+        // Optional header follows COFF header
+        IntPtr optAddr = coffAddr + 20;
+        byte[] optionalHeader = _memory.ReadBytes(optAddr, sizeOfOptionalHeader);
+        if (optionalHeader.Length < sizeOfOptionalHeader)
+            throw new InvalidDataException("Failed to read optional header.");
+
+        return (optionalHeader, null);
     }
 
     /// <summary>