Add prebuilt C++ shared library SDK (libopenwakeword_ax) + header for secondary development

Fix HF README: add YAML frontmatter, update tree/C++ section to prebuilt-only layout

Remove C++ sources/build scripts from HF release (keep precompiled binaries only)

Standardize HF model card metadata and replace classifiers with recalibrated axmodels

First commit

Update .gitattributes

initial commit