feat: Cardboard VR mode with ARM64 SteamVR (#704)

* feat: add Cardboard mode with side-by-side lens-distorted eyes and 3DoF head tracking

* fix: derive the Cardboard field of view from the panel and recentre fully when far from upright

* feat: share the Cardboard head pose with the guest and add a SteamVR driver for it

* feat: run SteamVR's compositor on Turnip/KGSL with a display-extension layer and a driver-direct HMD

* feat: show SteamVR frames in Cardboard mode through a driver-side presenter and a fake direct-mode display

* feat: install and start SteamVR for Cardboard mode from the session drawer

* docs: describe Cardboard mode and the SteamVR path

* feat: drive SteamVR hands from the game pad and keep the Cardboard headset out of standby

* docs: record where the SteamVR dashboard stops

* fix: map Cardboard head tracking to the screen's axes and keep turns about the real vertical as yaw

* fix: give Cardboard its previous picture back when SteamVR stops

* fix: report sem_otime from emulated SysV semaphores so SteamVR's web helper can start

* fix: bridge SteamVR's shared semaphores across processes and keep Steam alive while SteamVR runs

* feat: present SteamVR straight to DroidDeck's compositor at panel resolution

* docs: update Cardboard VR notes for the dashboard, semaphore bridge and direct presenter

* fix: keep Wine and FEX signal handlers in the VR layer; add semaphore tracing

* fix: clear a stale SteamVR active marker on status

* fix: clear only an old SteamVR active marker

* fix: unblock SteamVR clients on Turnip and keep Steam's web helper alive across SteamVR runs

* fix: judge shared waits before a submit's own signals and on Vulkan 1.0 devices

* docs: record VR games, SteamVR Home and OpenXR results on the Thor

* docs: add Cardboard VR learnings from the Thor bring-up

* docs: add Cardboard VR screenshots from the Thor

* fix: keep the VR layer's display stand-in to SteamVR runs and clear a leftover marker at session start

* fix: report SteamVR start and stop failures from the helper's exit code

.github/workflows/build.yml

@@ -186,7 +186,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: app/src/main/assets/linuxfs
-          key: preloads-${{ env.PRELOAD_CACHE_VERSION }}-${{ hashFiles('app/src/main/cpp/fakeinput_steam.cpp', 'app/src/main/cpp/adrenotools/src/hook/kgsl.h', 'tools/quest/*', 'tools/linuxfs/preload/*.c', 'tools/linuxfs/build-x86-preloads.sh', 'tools/linuxfs/fex/*', 'tools/linuxfs/clipboard/*.c', 'tools/linuxfs/ssbs/*.c', 'tools/proot/fastpath/*.c', 'tools/linuxfs/overlay/usr/local/bin/*', 'tools/linuxfs/overlay/usr/bin/**', 'tools/linuxfs/desktop/*', 'tools/gamescope/release.env', 'tools/wlroots/release.env', 'tools/linuxfs/uruntime.env', 'tools/linuxfs/licenses/*', 'tools/mangoapp/*', 'tools/msitools/**', 'tools/comet/**', 'tools/linuxfs/debian-image.env') }}
+          key: preloads-${{ env.PRELOAD_CACHE_VERSION }}-${{ hashFiles('app/src/main/cpp/fakeinput_steam.cpp', 'app/src/main/cpp/adrenotools/src/hook/kgsl.h', 'tools/quest/*', 'tools/linuxfs/preload/*.c', 'tools/linuxfs/build-x86-preloads.sh', 'tools/linuxfs/fex/*', 'tools/linuxfs/clipboard/*.c', 'tools/linuxfs/ssbs/*.c', 'tools/proot/fastpath/*.c', 'tools/linuxfs/overlay/usr/local/bin/*', 'tools/linuxfs/overlay/usr/bin/**', 'tools/linuxfs/desktop/*', 'tools/gamescope/release.env', 'tools/wlroots/release.env', 'tools/linuxfs/uruntime.env', 'tools/linuxfs/licenses/*', 'tools/mangoapp/*', 'tools/msitools/**', 'tools/comet/**', 'tools/linuxfs/debian-image.env', 'tools/vr/**') }}
 
       - name: Build libfakeinput.so and libblsession.so (glibc aarch64)
         if: steps.preloads.outputs.cache-hit != 'true'
@@ -218,6 +218,9 @@ jobs:
           mkdir -p "$D/usr/local/bin"
           aarch64-linux-gnu-gcc -O2 -Wall -Wextra -o "$D/usr/local/bin/droiddeck-clipboard" tools/linuxfs/clipboard/clipboard.c -ldl
           aarch64-linux-gnu-strip --strip-unneeded "$D/usr/local/bin/droiddeck-clipboard"
+          # Cardboard mode's SteamVR driver and Vulkan layer (tools/vr), Vulkan headers from the runner's NDK.
+          VK_INCLUDE=$(ls -d "${ANDROID_NDK_LATEST_HOME:-${ANDROID_NDK_HOME:-$ANDROID_NDK_ROOT}}"/toolchains/llvm/prebuilt/*/sysroot/usr/include | head -1) \
+            tools/vr/build.sh --native "$D/usr/local/lib/droiddeck-vr"
           for script in tools/linuxfs/overlay/usr/local/bin/droiddeck-* tools/linuxfs/overlay/usr/local/bin/steam-compatibility; do
             install -Dm644 "$script" "$D/usr/local/bin/$(basename "$script")"
           done