docs: add bugfix newsfragment and dags_needing_dagruns dataset docstring

Author: leossantos

airflow/models/dag.py

@@ -4069,6 +4069,11 @@ def dags_needing_dagruns(cls, session: Session) -> tuple[Query, dict[str, tuple[
         This will return a resultset of rows that is row-level-locked with a "SELECT ... FOR UPDATE" query,
         you should ensure that any scheduling decisions are made in a single transaction -- as soon as the
         transaction is committed it will be unlocked.
+
+        For dataset-triggered scheduling, DAGs that have ``DatasetDagRunQueue`` rows but no matching
+        ``SerializedDagModel`` row are omitted from the returned ``dataset_triggered_dag_info`` until
+        serialization exists; queue rows are **not** deleted here so the scheduler can re-evaluate on a
+        later run.
         """
         from airflow.models.serialized_dag import SerializedDagModel
 

newsfragments/63546.bugfix.rst

@@ -0,0 +1 @@
+Fix premature dataset-triggered DagRuns when ``SerializedDagModel`` was missing while ``DatasetDagRunQueue`` still had rows for that DAG; queue entries are kept for the next evaluation.