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

crates/init/src/devices.rs

@@ -62,6 +62,15 @@ pub fn system_control() -> Option<CapSlot> {
     slot(info.system_control_slot)
 }
 
+/// The console capability, until init hands it to the log server.
+pub fn console() -> Option<CapSlot> {
+    let info = boot_info();
+    if info.magic != types::bootinfo::MAGIC {
+        return None;
+    }
+    slot(info.console_slot)
+}
+
 /// Sorts the board's devices out.
 pub fn discover() -> Devices {
     let info = boot_info();