Publish standalone Apache Airflow Mypy documentation

[hussein-awala]

Publish independently versioned Sphinx documentation for apache-airflow-mypy and wire it into the documentation build, versioning, publishing, selective-check, and release workflows.

The core static type-checking page now points to the standalone package documentation so plugin guidance and release notes follow the plugin's own release cadence.

Companion site-index PR: apache/airflow-site#1633

Validation:

• Standalone Sphinx build and spellcheck
• 385 targeted unit tests, plus the stable-version script tests
• Pre-commit checks for the complete diff
• Manual checks, except the mypy manual hook could not start Breeze because the local Colima socket is unavailable

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

• Yes — Pi 0.84.2

Generated-by: Pi 0.84.2 following the guidelines

[github-actions]

Backport failed to create: v3-3-test. View the failure log Run details

Note: As of Merging PRs targeted for Airflow 3.X
the committer who merges the PR is responsible for backporting the PRs that are bug fixes (generally speaking) to the maintenance branches.

In matter of doubt please ask in #release-management Slack channel.

Status	Branch	Result
❌	v3-3-test

You can attempt to backport this manually by running:

cherry_picker 29c3ac2 v3-3-test

This should apply the commit to the v3-3-test branch and leave the commit in conflict state marking
the files that need manual conflict resolution.

After you have resolved the conflicts, you can continue the backport process by running:

cherry_picker --continue

If you don't have cherry-picker installed, see the installation guide.