Support 32-bit (win32) OpenXR runtime

[dfattal]

Context

DisplayXR currently ships a 64-bit runtime only (DisplayXR_win64.json + DisplayXRClient.dll x64). There is no win32 runtime DLL or manifest.

Historically the 32-bit OpenXR active-runtime key on Windows
(HKLM\Software\WOW6432Node\Khronos\OpenXR\1\ActiveRuntime) was pointed
at Leia's Monado-based SRMonado runtime as a stopgap for 32-bit OpenXR
clients. SRMonado is now deprecated and has been removed, and the 32-bit
key has been cleared. As a result, 32-bit OpenXR applications currently
have no active runtime on a DisplayXR-only machine.

Ask

If/when we decide to support 32-bit OpenXR clients, we need to:

• Build a 32-bit (win32) DisplayXRClient.dll + dependencies
• Emit a DisplayXR_win32.json runtime manifest
• Register it under HKLM\Software\WOW6432Node\Khronos\OpenXR\1\ActiveRuntime in the installer
• Verify the 32-bit native compositors (at minimum D3D11) build and run under win32
• CI: add a win32 build/leg or compile-check

Priority

Low / future. Modern OpenXR apps (game engines, demos) are predominantly
64-bit; tracking this so the gap is explicit rather than silently broken.