separates platform-specific code into hal-posix-io and hal-win-io gems,
making mruby-io platform-independent. HAL interface defined in
mrbgems/mruby-io/include/io_hal.h covers file operations, I/O operations,
and process operations. follows mruby-task dependency pattern where HAL
gems depend on feature gem. ws2_32 library linked in hal-win-io gem.
Co-authored-by: Claude <noreply@anthropic.com>
Yukihiro "Matz" Matsumoto