=== Same-thread binding: visible to direct AND indirect callees ===
handleRequest(): REQUEST_ID.get() = req-42
logSomewhereDeeper() (indirect callee, same thread): REQUEST_ID.get() = req-42

=== Outside any binding: isBound() is false ===
main: REQUEST_ID.isBound() = false

=== A plain `new Thread()` does NOT inherit the binding ===
plain child thread: REQUEST_ID.isBound() = false

=== A StructuredTaskScope.fork()'d thread DOES inherit the binding ===
forked subtask: REQUEST_ID.isBound() = true, REQUEST_ID.get() = req-100
done