Add enqueue path to sched_enqueue_task()

Previously, `sched_enqueue_task()` only marked task state as TASK_READY
to represent the task has been enqueued due to the original scheduler
selects the next task based on the global list and all tasks are kept in
it.

After new data structure, ready_queue[], is added for keeping runnable
tasks, the enqueuing task API should push the embedded linkage list node,
rq_node, into the corresponding ready_queue.

This commit uses list_pushback_node() helper to enqueue the embeded list
node of tcb into ready queue and sets up cursor and bitmap of the
corresponding priority queue.

Author: vicLin8712

kernel/task.c

@@ -74,7 +74,7 @@ static const uint8_t priority_timeslices[TASK_PRIORITY_LEVELS] = {
     TASK_TIMESLICE_IDLE      /* Priority 7: Idle */
 };
 
-/* Mark task as ready (state-based) */
+/* Enqueue task into ready queue */
 static void sched_enqueue_task(tcb_t *task);
 
 /* Utility and Validation Functions */
@@ -357,17 +357,36 @@ void _yield(void) __attribute__((weak, alias("yield")));
  * practical performance with strong guarantees for fairness and reliability.
  */
 
-/* Add task to ready state - simple state-based approach */
+/* Enqueue task into ready queue */
 static void sched_enqueue_task(tcb_t *task)
 {
     if (unlikely(!task))
         return;
 
+    uint8_t prio_level = task->prio_level;
+
     /* Ensure task has appropriate time slice for its priority */
-    task->time_slice = get_priority_timeslice(task->prio_level);
+    task->time_slice = get_priority_timeslice(prio_level);
     task->state = TASK_READY;
 
-    /* Task selection is handled directly through the master task list */
+    list_t **rq = &kcb->ready_queues[prio_level];
+    list_node_t **cursor = &kcb->rr_cursors[prio_level];
+
+    if (!*rq)
+        *rq = list_create();
+
+    list_pushback_node(*rq, &task->rq_node);
+
+    /* Setup first rr_cursor */
+    if (!*cursor)
+        *cursor = &task->rq_node;
+
+    /* Advance cursor when cursor same as running task */
+    if (*cursor == kcb->task_current)
+        *cursor = &task->rq_node;
+
+    kcb->ready_bitmap |= (1U << (task->prio_level));
+    return;
 }
 
 /* Remove task from ready queues - state-based approach for compatibility */