Updated the cheatsheet to clearly explain that `add` creates thread-local
scoped variables while `add_global`, `add_global_const`, and `set_global`
create global variables shared between all threads. Added a summary table
comparing scope, thread safety, and conflict behavior. Also added a test
exercising the key behavioral differences between these methods.
Co-authored-by: leftibot <leftibot@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
