Steam Frame build, packaging and deployment scripts; render test

- build_scripts/steamframe/: Debian trixie (Qt 6.8) containers for the
  aarch64 cross build, native build and tests; toolchain; scripts to build,
  test (Vulkan validation layers), package (system Qt, ~3 MB) and deploy over
  SSH. Adapted from the vrdashboard template.
- test/render/: render test for the OpenGL and Vulkan backends, driven like
  OverlayController (option OVRAS_BUILD_TESTS).
- RPATH only $ORIGIN, without the build machine's link directories.
- Ignore dist/.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

build_scripts/steamframe/native.Dockerfile

@@ -0,0 +1,19 @@
+# Native build environment (any architecture). On x86_64 it is the base of the
+# test container (test.Dockerfile); on the Steam Frame itself (aarch64, e.g.
+# with podman) it builds the same package as the cross build. Debian trixie
+# ships Qt 6.8, the series of the Frame's system Qt. Adapted from the
+# vrdashboard template.
+FROM debian:trixie
+
+ENV LANG=C.UTF-8
+
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends \
+        ca-certificates cmake ninja-build pkgconf file g++ \
+        qt6-base-dev qt6-base-dev-tools qt6-declarative-dev qt6-declarative-dev-tools \
+        qt6-multimedia-dev qt6-websockets-dev qt6-svg-dev \
+        libgl-dev libegl-dev libvulkan-dev libxkbcommon-dev \
+        libx11-dev libxt-dev libxtst-dev libpulse-dev \
+        qml6-module-qtquick qml6-module-qtqml-workerscript qml6-module-qtquick-window \
+        qt6-qpa-plugins \
+ && rm -rf /var/lib/apt/lists/*