fix(scheduler): load dag_run eagering for execution API validation

[Lee-W]

Why

Closes: #56763

how to reproduce (through breeze on e24cfb0)

1. Add the following lines to files/airflow-breeze-config/environment_variables.env

AIRFLOW__SCHEDULER__TASK_INSTANCE_HEARTBEAT_TIMEOUT=1
AIRFLOW__SCHEDULER__TASK_INSTANCE_HEARTBEAT_TIMEOUT_DETECTION_INTERVAL=5

2. Add the following dag to files/dags

Dag

from __future__ import annotations

import os
import time

import pendulum

from airflow.sdk import Asset, Metadata, dag, task

asset = Asset("test")


@dag(schedule=None, start_date=pendulum.datetime(2025, 1, 1), catchup=False)
def producer():
    @task(outlets=[asset])
    def producer_task():
        yield Metadata(asset=asset, extra={"test": 1})

    producer_task()


@dag(schedule=asset, start_date=pendulum.datetime(2025, 1, 1), catchup=False)
def consumer():
    @task()
    def consumer_task(ds_str):
        print(ds_str)
        time.sleep(5)
        os._exit(1)  # immediate exit, no cleanup, no heartbeat

    consumer_task("{{ (triggering_asset_events.values() | first | last).extra }}")


producer()
consumer()

3. breeze start-airflow --db-reset --backend postgres
4. Turn on both produer and conumser Dags
5. Continously trigger producer (10 ~ 20 times) really quick

What

Kaxil implemented a _eager_load_dag_run_for_validation method to ensure that dag_run exists even when a ti becomes a zombie task

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[kaxil]

Were you able to reproduce the error & does this fix it. (It should but worth verifying)

[Lee-W]

Were you able to reproduce the error & does this fix it. (It should but worth verifying)

yep, I'm now simplifying the sample code I used and will add to the desciprion

[Lee-W]

Updated the Dag and steps I used in detail

[potiuk]

Hey @Lee-W -> we had to revert it as it fails for Python 3.13. Can you please re-do it (and set all versions label on PR to trigger the tests for 3.13.

See https://github.com/apache/airflow/actions/runs/18676364216/job/53249204014