Return each attempt's own URL from operator extra links

[1fanwang]

Operator extra links keep only the latest attempt's URL. After a retry, attempt 1 can open attempt 2's logs.

Closes: #71471

Why

The link reader ignores the key's attempt number. The execution API clears task XComs before each attempt, so the row belongs to the latest attempt.

What

The task runner writes each rendered link to the task state store under an attempt key. The reader checks it first and falls back to XCom for older links.

Tests

This SQLite probe stores attempt 1 in the state store and attempt 2 in XCom:

Probe and output

T=airflow-core/tests/test_operator_link_attempt_probe.py
cat >"$T" <<'PY'
import json, pytest
from airflow._shared.state import TaskScope
from airflow.models.xcom import XComModel
from airflow.serialization.definitions.operatorlink import XComOperatorLink
from airflow.state import get_state_backend
@pytest.mark.db_test
def test_probe(session, create_task_instance):
    t = create_task_instance(task_id="link")
    ids = dict(dag_id=t.dag_id, run_id=t.run_id, task_id=t.task_id, map_index=t.map_index)
    get_state_backend().set(TaskScope(**ids), "_link_attempt_1__link_MyLink", json.dumps("https://logs/attempt-1"), session=session)
    XComModel.set(key="_link_MyLink", value="https://logs/attempt-2", session=session, **ids)
    session.commit()
    link = XComOperatorLink(name="My Link", xcom_key="_link_MyLink")
    for n in (1, 2):
        print(f"try {n} -> {link.get_link(None, ti_key=t.key._replace(try_number=n))}")
PY

git worktree add --detach /tmp/airflow-71522-main upstream/main
cp "$T" "/tmp/airflow-71522-main/$T"
(cd /tmp/airflow-71522-main && AIRFLOW_HOME=/tmp/af-main uv run --project airflow-core pytest "$T" -s -q --no-cov)
AIRFLOW_HOME=/tmp/af-head uv run --project airflow-core pytest "$T" -s -q --no-cov

upstream/main:
try 1 -> https://logs/attempt-2
try 2 -> https://logs/attempt-2

this PR:
try 1 -> https://logs/attempt-1
try 2 -> https://logs/attempt-2

Risk

The task state scope has no attempt field, so the key includes the attempt number. Existing XCom writes and fallback behavior remain unchanged.

Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

Generated-by: GitHub Copilot CLI (GPT-6 Astra) following the guidelines

[ashb]

@amoghrajesh Can you take a look at this, it is like trying to fix the same issue as #73315

[1fanwang]

Closing in favor of #73315 — @amoghrajesh's fix solves the same problem (operator extra links surviving across retries) with a simpler, self-contained approach: per-try-suffixed XCom keys plus skipping those keys during XCom clearing. Mine additionally depended on the task-state-store abstraction from #71307/#68936, which is still pending consensus on the mailing list, so 73315 is the better fix to land.