docs: virtio-gpu + virgl assessment — honest state, linux-7.0 cache protected

Virtio-gpu display driver (217 lines) exists in redox-drm — KMS, GEM,
page flip all work. QEMU display path functional.

Mesa virgl (3D acceleration for QEMU):
- Build attempted with -Dgallium-drivers=swrast,virgl
- Reaches 932/1104 objects
- Blocked: virgl_screen.c int-conversion errors, vtest winsys needs
  bits/safamily-t.h
- Reverted to swrast-only for stability
- Remaining virgl port documented as WIP

Linux 7.0 kernel source:
- Cloned to local/linux-kernel-cache/linux-7.0 (durable, survives clean)
- Symlinked from build/linux-kernel-cache/linux-7.0
- Added to .gitignore (embedded repo)
- Drivers/gpu/drm/virtio/ available for virgl protocol reference

.gitignore

@@ -84,3 +84,4 @@ local/cache/pkgar/
 Packages/redbear-firmware.pkgar
 packages/
 sources/
+local/linux-kernel-cache/

local/docs/CONSOLE-TO-KDE-DESKTOP-PLAN.md

@@ -113,10 +113,16 @@ The kernel handles 35 syscalls explicitly. Remaining gaps:
 | Component | Status | Detail |
 |-----------|--------|--------|
 | mesa | 🟡 Builds | llvmpipe software renderer; EGL=on, GBM=on, GLES2=on |
+| mesa virgl (QEMU 3D) | 🔴 WIP | Build attempted — virgl_screen.c int-conversion errors; vtest winsys needs `bits/safamily-t.h`; requires Mesa source patches for Redox target |
 | radeonsi (AMD HW) | 🔴 Not built | Not cross-compiled for Redox target |
 | iris (Intel HW) | 🔴 Not built | Not cross-compiled for Redox target |
 | OSMesa | 🟢 Builds | Off-screen software rendering |
 
+**virgl path**: Mesa `-Dgallium-drivers=swrast,virgl` compilation reaches 932/1104 objects.
+Remaining work: (1) fix `virgl_screen.c` int-conversion warnings-as-errors on Redox target,
+(2) provide `bits/safamily-t.h` or disable vtest winsys,
+(3) integrate virgl drm winsys with redox-drm CS ioctl backend.
+
 **Blocker**: Mesa hardware renderer cross-compilation requires CS ioctl backend + validation hardware.
 
 ### 2.3 Hardware GPU — The Big Gap