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>

.clang-format

@@ -0,0 +1,7 @@
+# Google C++ style (https://google.github.io/styleguide/cppguide.html): 2-space indent,
+# 80 columns, opening braces on the same line everywhere (functions included).
+---
+Language: Cpp
+BasedOnStyle: Google
+Standard: Latest
+...