Moves the existing virtual-thread/context-propagation project into
context-propagation/ and adds method-security/ for the Spring Security 7
method-security article: nine runnable demos, fourteen assertions, and every
transcript the article quotes, regenerated by scripts/run-all.sh.
Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01RSrsDSRKVsY588yFiMJMo9
