docs: clarify role as raw archive and link to curated unofficial dataset

README: document Windows MSVC (Detours, WinSparkle) & The Powder Toy integration

Update repo references to decbench-cpp-dataset-unofficial

README: document full C++ corpus (1,103 binaries across 40 projects)

Expand C++ corpus to 1,103 binaries across 40 Tier-A projects

README: document cpp-compiled corpus

Add compiled C++ corpus (snappy, double-conversion, ninja x O0/O2/O2-noinline)

Initial upload: C++ target qualification workspace (unofficial)

initial commit