fix: Windows stack arguments for >4 args

[kolkov]

Summary

• Fixes critical panic when calling C functions with >4 arguments on Windows
• Functions like vkCreateGraphicsPipelines (6 args) now work correctly
• Simplified Windows FFI by removing intermediate wrapper

Problem

After v0.3.4 fix for stack overflow, functions with >4 arguments caused:

panic: stack arguments not implemented

Win64 ABI passes:

• First 4 args: RCX, RDX, R8, R9 (registers)
• Args 5+: on stack

The previous implementation only handled 4 register args.

Solution

Use syscall.SyscallN(fn, args...) with variadic arguments:

• Supports unlimited arguments (tested up to 15+)
• Handles both register and stack arguments automatically
• Same approach used by purego

Changes

• internal/arch/amd64/call_windows.go - Use SyscallN directly with args...
• internal/syscall/syscall_windows_amd64.go - Removed (no longer needed)
• CHANGELOG.md - Added v0.3.5 entry

Test Plan

• All tests pass (89.6% coverage)
• Pre-release script passes
• FFI overhead: ~64 ns/op (improved)
• Manual Vulkan testing with >4 arg functions

Affected Vulkan Functions

• vkCreateGraphicsPipelines (6 args)
• vkCmdBindVertexBuffers (5 args)
• vkCmdCopyBuffer (5 args)
• Many others with >4 parameters