=== Demo 6: DelegatingSecurityContextTaskScheduler and the synthetic system identity ===
A) schedule() called with NO context present on the caller thread: NO AUTHENTICATION (lost)  [this is the realistic startup case the post warns about]
B1) first schedule() call, caller context = registration-thread-X: authenticated as registration-thread-X
B2) second schedule() call on the SAME wrapper, caller context changed to registration-thread-Y: authenticated as registration-thread-Y  [independent per-call capture, not frozen at wrapper construction]
C) task body sets its own systemContext(), ignoring anything the scheduler wrapper captured: SYSTEM with authorities [ROLE_SYSTEM]
EDGE) AuthenticationTrustResolver.isAnonymous(systemContext()): false  [false -- SYSTEM is a normal authenticated principal, not Spring Security's anonymous concept]
