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/kernel/src/interrupt.rs

@@ -1,6 +1,6 @@
 use domain::scheduler::{Scheduler, SchedulerDecision};
 use platform::Platform;
-use types::id::{CoreId, IrqId, ThreadId};
+use types::id::CoreId;
 
 use crate::Kernel;
 
@@ -53,22 +53,4 @@ impl<P: Platform> Kernel<P> {
             self.scheduler.tick(core, current_tid)
         }
     }
-
-    pub fn handle_interrupt(&mut self, irq: IrqId) -> Option<ThreadId> {
-        self.platform.mask_irq(irq);
-
-        let tid = self.irqs.owner(irq)?;
-        let thread = self.threads.get_mut(tid).ok()?;
-
-        if !matches!(thread.state(), domain::thread::ThreadState::Blocked(_)) {
-            return None;
-        }
-
-        let priority = thread.priority();
-        let core = self.platform.core_id();
-        let _ = thread.unblock();
-        self.scheduler.add(tid, priority, core);
-
-        Some(tid)
-    }
 }