Add atomic block helper for mutex lock

Previously, mutex_block_atomic() only updated the task state. Under the new
scheduler design, the blocked task must also be removed from the ready queue.

The existing helper _sched_block() does not match the mutex path because it
operates on queue_t instead of list_t and also processes deferred timer work,
which mutex locking does not require.

This commit introduces _sched_block_mutex(), a helper that supports the list-
based waiter structure and skips deferred timer handling. It will be used by
the mutex lock APIs in a later change.

Author: vicLin8712

include/sys/task.h

@@ -301,6 +301,9 @@ uint64_t mo_uptime(void);
  */
 void _sched_block(queue_t *wait_q);
 
+/* Support mutex data structure */
+void _sched_block_mutex(list_t *waiters);
+
 /* Application Entry Point */
 
 /* The main entry point for the user application.

kernel/task.c

@@ -1102,3 +1102,22 @@ void _sched_block(queue_t *wait_q)
     self->state = TASK_BLOCKED;
     _yield();
 }
+
+void _sched_block_mutex(list_t *waiters)
+{
+    if (unlikely(!waiters || !kcb || !kcb->task_current ||
+                 !kcb->task_current->data))
+        panic(ERR_SEM_OPERATION);
+
+    tcb_t *self = kcb->task_current->data;
+
+    /* Remove node from ready queue */
+    sched_dequeue_task(self);
+
+    if (list_pushback(waiters, self) != 0)
+        panic(ERR_SEM_OPERATION);
+
+    /* set blocked state - scheduler will skip blocked tasks */
+    self->state = TASK_BLOCKED;
+    _yield();
+}