Implement IntPtr.Size and sizeof(nint) for the 6502

[jonathanpeppers]

Fixes #33

The 6502 is an 8-bit CPU, so IntPtr.Size returns 1.

Two IL patterns are handled:

• IntPtr.Size emits call IntPtr::get_Size() → handled in the Call switch as a compile-time constant (LDA #1)
• sizeof(nint) emits the Sizeof IL opcode → new case in the int operand handler (LDA #1)

Both produce identical output: a single LDA # instruction.

Example usage

byte size = (byte)IntPtr.Size;     // size = 1 on NES
pal_col(0, size);

Tests added

• IntPtrSize — verifies IntPtr.Size emits LDA #
• SizeofNint — verifies sizeof(nint) emits LDA #

All 307 tests pass.

[Copilot]

Pull request overview

This PR implements support for IntPtr.Size and sizeof(nint) in the dotnes transpiler, resolving issue #33. On the 6502 (an 8-bit CPU), the native integer size is 1 byte, so both expressions produce LDA #$01.

Changes:

• Added a Sizeof IL opcode handler in IL2NESWriter.Write(ILInstruction, int) that emits LDA #1
• Added an IntPtr.get_Size case in the Call handler in IL2NESWriter.Write(ILInstruction, string) that emits LDA #1
• Added two Roslyn-based tests (IntPtrSize and SizeofNint) verifying the output contains A901 (LDA #$01)

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/dotnes.tasks/Utilities/IL2NESWriter.cs	Added Sizeof opcode case (line 1225) and IntPtr.get_Size call case (line 1762), both emitting WriteLdc(1)
src/dotnes.tests/RoslynTests.cs	Added two test methods verifying that IntPtr.Size and sizeof(nint) produce the expected LDA #$01 instruction