Checkpoint 09: backend policy and Linux .elf packaging
Parent: PHLEGM-v8-Developer-Distribution-Gfx-Matrix-08-2026-1007-1523-3332.zip

Canonical target policy:
- Windows 32bit/64bit: OpenGL or D3D11. Windows Vulkan is rejected.
- Linux x86/x86_64: OpenGL or Vulkan; D3D11 remains an accepted compatibility selection and is forwarded to the Vulkan presenter.
- Linux executables use .elf; Windows executables use .exe.

Implementation:
- Master platform metadata, build selection/validation, installer selection/validation and End-User packaging now agree on the OS-specific backend policy.
- Linux D3D11 presentation uses the Vulkan SDL window/swapchain path rather than DXVK Native. Runtime dependency packaging no longer requires DXVK Native for that compatibility selection.
- Package-PHLEGM-v8.ps1 now requires canonical Linux .elf executable names and accepts Linux D3D11 compatibility packages.
- Existing native tree.lib/archive.lib behavior, tree/icons mode, native/CHR GUI font switch, PPU/APU Skip controls, and FPS/frame-skip overlay are retained.

Validation performed in this environment:
- Shell syntax checks PASS for PHLEGM-Linux-Compiler.sh and Native-Linux-Compile.sh.
- Active target/package metadata consistency inspected after edits.
- tree.lib/archive.lib source scan shows no PowerShell/pwsh/7z/unzip/zip.exe/Shell external archive operations.
- Text newline policy retained: CRLF for normal project text, LF for .sh.

Limitations carried forward:
- This container does not currently expose fbc on PATH, so checkpoint 09 does not claim a fresh native FreeBASIC compile. Checkpoint 08 compile diagnostics remain included as historical evidence only.
- Vulkan graphical runtime, Windows native link/runtime, and Linux x86 runtime still require suitable target runtime environments.
