PHLEGM v8 Host/GFX Boundary Checkpoint
Timestamp: 2026-1007-1257-5695 (America/Phoenix)

Captured milestone:
  - Canonical host entry points added:
      host_windows_32.lib
      host_windows_64.lib
      host_linux_x86.lib
      host_linux_x86_64.lib
  - Canonical graphics entry points added:
      gfx_opengl.lib
      gfx_d3d11.lib
      gfx_vulkan.lib
  - host.lib selects exactly one OS/architecture host library.
  - gfx.lib selects exactly one renderer backend.
  - D3D11 is compile-time restricted to Windows; Vulkan to Linux.
  - PHLEGM.bas no longer directly includes/links Win32 host libraries.
  - Shared MachineDisplaySurface.windowHandle is now opaque HostWindowHandle.
  - host-types.bi establishes architecture-neutral shared handle/rectangle types.
  - Existing SuperPET/MC6809 and Linux build-system work is preserved.

Next migration slice:
  - Route keyboard/session/display host calls through the selected host library.
  - Continue removing direct Win32 types/APIs from shared source files.
