Meltano

<https://github.com/meltano/sdk/pull/3838|#3838 docs: Fix cross-reference warning in BATCH guide page>
Pull request opened by <https://github.com/edgarrmondragon|edgarrmondragon>
SSIA

*Summary by Sourcery*

Fix BATCH guide cross-references and enforce warning-free documentation builds.
Bug Fixes:
• Fix the cross-reference warning in the BATCH messages documentation page.
Enhancements:
• Enable warning-as-error documentation builds to catch Sphinx issues.
Documentation:
• Configure heading anchors for the BATCH messages guide.
<https://github.com/meltano/sdk|meltano/sdk>

<https://github.com/meltano/sdk/pull/3838|#3838 docs: Fix cross-reference warning in BATCH guide page>
Pull request merged by <https://github.com/edgarrmondragon|edgarrmondragon>
<https://github.com/meltano/sdk|meltano/sdk>