Improve the default SMTP task failure email template

[wilmerdooley]

Resolves #61667.

The default email that SmtpNotifier sends on task failure does not show which DAG or task failed, so it is hard to triage at a glance. This restyles the default templates for readability, keeping the change minimal and backward compatible.

What changed

• templates/email.html: add DAG and Task rows (previously missing) alongside the existing Run ID, Try, State, Host and log link, and lay the body out as a scannable table. Layout uses a plain <table> with inline cell styles only (no <style> or <head> styling, no CSS grid or flexbox), so it renders consistently in Gmail and Outlook.
• templates/email_subject.jinja2: a more scannable subject, [Airflow] {{ ti.dag_id }}.{{ ti.task_id }} {{ ti.state }} - Run {{ ti.run_id }}. The SLA branch is unchanged.
• tests/unit/smtp/notifications/test_smtp.py: update the one assertion that pins the default subject.

Scope and compatibility

• Only the SMTP provider default templates are touched. airflow-core and task-sdk are left alone, since email integration is moving out of core (PR [WIP] Migrate core EmailOperator to SMTP provider #30531).
• Backward compatible: a user-provided subject_template or html_content_template (connection extras) still takes precedence over the bundled defaults.

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

• Yes (please specify the tool below)

Generated-by: Claude Code

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Important

🛠️ Maintainer triage note for @wilmerdooley · by @potiuk · 2026-07-28 16:10 UTC

Helpful heads-up from the maintainers — please address before this PR can be reviewed:

• ❌ Unit tests. See docs.

The ball is in your court — you've been assigned to this PR. Fix the above, then mark it Ready for review.

See the Pull Request quality criteria for how to fix each item. There is no rush.

Note: your branch is 1310 commits behind main — please rebase and push again to get up-to-date CI results.

_{Automated triage — may be imperfect; a maintainer takes the next look. We use this two-stage triage process so maintainers' limited time goes to the conversation with you.}

[eladkal]

Can you please add before and after images if the template?

[wilmerdooley]

Before/after renders of the default task-failure email, with the same sample failure context in both:

Before (main):

After (this PR): adds DAG and Task rows and lays the fields out as a card with a header and a View Logs button.

[wilmerdooley]

I looked into the two red checks and they aren't coming from this change. Both failed during the runner setup step ("Cleanup repo"), before the code was even checked out, when the runner tried to pull the bash:latest image and the Docker Hub pull timed out (exit 125). Because that setup step failed, the checkout and all the actual test steps were skipped rather than run, so the tests never executed in those two jobs. Everything else is green, including the smtp unit tests in the other matrix jobs.

A re-run of just those two jobs should clear them, but I can't trigger that myself as an external contributor. How would you prefer to proceed? Happy to rebase onto current main and push if a fresh commit is the easier way to re-trigger CI, though that's your call.