Initial FrameAssistant baseline from the vrdashboard template

Template stripped to the overlay platform (examples, demo UI and Frame
test package removed), renamed to FrameAssistant, and working rules for
the project recorded in CLAUDE.md.

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

docker/test.Dockerfile

@@ -0,0 +1,9 @@
+# Test environment on top of docker/native.Dockerfile: Mesa Vulkan/GL drivers (incl. the
+# lavapipe software rasterizer), Khronos validation layers and Xvfb. See scripts/container-test.sh.
+FROM frameassistant-build-native
+
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends \
+        mesa-vulkan-drivers vulkan-validationlayers vulkan-tools libgl1-mesa-dri \
+        xvfb xauth fonts-dejavu-core \
+ && rm -rf /var/lib/apt/lists/*