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/domain/src/error.rs

@@ -33,4 +33,9 @@ pub enum KernelError {
     InvalidRegion,
     /// The object a capability would refer to no longer exists.
     NoSuchObject,
+    /// The capability names the wrong kind of object for this operation.
+    WrongObject,
+    /// `Reply` with an empty reply slot, or a call whose reply was dropped.
+    NoReply,
+    InvalidArgument,
 }