Kernel: Panic if ^C is followed by ^Z too quickly

^C followed by ^Z too quickly sometimes ends in a panic, at least on riscv64 ``` [python3.14(59:59)]: KERNEL PANIC! :^( [python3.14(59:59)]: Attempting to stop with invalid thread state - Dying [python3.14(59:59)]: at ./Kernel/Tasks/Thread.cpp:1218 in void Kernel::Thread::set_state(State, u8) Kernel + 0x00000000003193c4 Kernel::__panic(char const*, unsigned int, char const*) +0x138 Kernel + 0x0000000000453a7e Kernel::Thread::set_state(Kernel::Thread::State, unsigned char) +0x3d4 Kernel + 0x000000000045934c Kernel::Thread::dispatch_signal(unsigned char) +0xa38 Kernel + 0x000000000045b01a Kernel::Thread::check_dispatch_pending_signal(Kernel::YieldBehavior) +0xd0 Kernel + 0x00000000000077c0 Kernel::ProcessorBase::exit_trap(Kernel::TrapFrame&, bool) +0x82 Kernel + 0x00000000004911ca restore_context_and_sret +0x0 ```