Function read_kmsg 

pub fn read_kmsg() -> String

Read the kernel ring buffer (equivalent to dmesg --notime). Exposed as pub so scenario tests that need to assert on kernel-log content (e.g. the sched_ext stall duration emitted by scx_exit(SCX_EXIT_ERROR_STALL) in kernel/sched/ext.c) can read the same buffer the framework captures into AssertResult::details on scheduler-died failures.