ci: Build Frame Home in CI

Build Frame Home payload in CI

Build the ARM64 headset payload against the glibc 2.39 baseline, validate its ABI,
and pass the generated artifact to Studio packaging.

Add provenance attestations and document CI and local build modes.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/openvr_loader.cpp

@@ -75,7 +75,11 @@ const char* kLibName = "openvr_api.dll";
 using Lib = void*;
 Lib open(const fs::path& p) { return dlopen(p.c_str(), RTLD_NOW | RTLD_LOCAL); }
 void* symbol(Lib l, const char* name) { return dlsym(l, name); }
+#if defined(__aarch64__)
+const char* kLibInRuntime = "bin/linuxarm64/libopenvr_api.so";
+#else
 const char* kLibInRuntime = "bin/linux64/libopenvr_api.so";
+#endif
 const char* kLibName = "libopenvr_api.so";
 #endif