feat(kernel): seL4-style IPC, notifications, status ABI

- badges + Mint, Call/Reply/ReplyRecv w/ gen-checked reply slot
- cap transfer (1/msg, copy, needs Delegate, rechecked at delivery)
- notifications: signal/wait/poll/bind, irq -> notification routing
- WaitAny/WaitForInterrupt removed; a0=status, ErrorCode
- libkos: single ecall primitive, compat wrappers + typed new api
- fix: trap return clobbered user t0 on every trap
- fix: wait queues FIFO, delegate keeps badge, fault cap checked
- docs/ipc.md spec, ipc tests, ipc fuzz, kani ntfn + waitqueue

crates/libkos/src/alloc_impl.rs

@@ -80,13 +80,17 @@ impl AllocatorInner {
                     if prev.is_null() {
                         self.free_list = new_block;
                     } else {
-                        unsafe { (*prev).next = new_block; }
+                        unsafe {
+                            (*prev).next = new_block;
+                        }
                     }
                 } else {
                     if prev.is_null() {
                         self.free_list = block.next;
                     } else {
-                        unsafe { (*prev).next = block.next; }
+                        unsafe {
+                            (*prev).next = block.next;
+                        }
                     }
                 }