Refactor mo_task_spawn() for O(1) scheduler support

Previously, mo_task_spawn() only created a task and appended it to the
global task list (kcb->tasks), assigning the first task directly from
the global list node.

This change adds a call to sched_enqueue_task() within the critical
section to enqueue the task into the ready queue and safely initialize
its scheduling attributes. The first task assignment is now aligned
with the RR cursor mechanism to ensure consistency with the O(1)
scheduler.

Author: vicLin8712

kernel/task.c

@@ -666,8 +666,12 @@ int32_t mo_task_spawn(void *task_entry, uint16_t stack_size_req)
     tcb->id = kcb->next_tid++;
     kcb->task_count++; /* Cached count of active tasks for quick access */
 
-    if (!kcb->task_current)
-        kcb->task_current = node;
+    /* Push node to ready queue */
+    sched_enqueue_task(tcb);
+    if (!kcb->task_current) {
+        kcb->task_current = kcb->harts->rr_cursors[tcb->prio_level];
+        tcb->state = TASK_RUNNING;
+    }
 
     CRITICAL_LEAVE();
 
@@ -681,7 +685,6 @@ int32_t mo_task_spawn(void *task_entry, uint16_t stack_size_req)
 
     /* Add to cache and mark ready */
     cache_task(tcb->id, tcb);
-    sched_enqueue_task(tcb);
 
     return tcb->id;
 }