feat(kernel): object lifetimes via slot generations

- SlotGenerations per table, never wraps, retires exhausted slots
- caps to dead/reused process, endpoint, region rejected
- endpoints owned, die w/ owner, waiters woken w/ error
- DropCap syscall + libkos wrapper
- irq table bounds-checked, routes dropped w/ thread
- self-kill terminates caller, exit_thread full cleanup
- sched run_now: switch to named thread, not queue head
- lifetime tests, fuzz kills/recreates, kani gen proofs

crates/kernel/src/tests/mod.rs

@@ -7,6 +7,7 @@ mod invariants;
 mod ipc;
 mod isolation;
 mod lifecycle;
+mod lifetimes;
 mod memory;
 mod simple;
 mod tick;