feat(kernel): console cap gates DebugPutchar, no uart fast path; spawn start arg in a0; delegate returns slot

crates/adapter-riscv/src/trap/fast.rs

@@ -3,7 +3,7 @@ use super::{TrapFrame, write_result};
 /// Syscalls answered without the kernel lock because they touch nothing it
 /// guards. A pending IPI or reschedule request forces the slow path.
 pub(super) fn fast_syscall(frame: &mut TrapFrame) -> bool {
-    use types::syscall_abi::{SYS_DEBUG_PUTCHAR, SYS_GET_PROCESS_ID, SYS_GET_TIME, SYS_YIELD};
+    use types::syscall_abi::{SYS_GET_PROCESS_ID, SYS_GET_TIME, SYS_YIELD};
     if crate::smp::has_pending_request() {
         return false;
     }
@@ -13,10 +13,6 @@ pub(super) fn fast_syscall(frame: &mut TrapFrame) -> bool {
             Some(pid) => kernel::SyscallResult::Value(pid),
             None => return false,
         },
-        SYS_DEBUG_PUTCHAR => {
-            crate::hw::uart::Uart::new().put_char(frame.regs[10] as u8);
-            kernel::SyscallResult::Ok
-        }
         SYS_YIELD if crate::smp::yield_is_noop() => kernel::SyscallResult::Ok,
         _ => return false,
     };