DEVOPS-1131: Use ref_name and add release tag validation in python_deploy_prod.yml

[RomFloreani]

DEVOPS-1131 - python_deploy_prod workflow to use tag from revision: no manual input
Use github.ref_name instead of workflow_dispatch input release-tag, and add a validate-release-tag job to fail fast when the workflow is not run from a tag.

Mirrors the change made in MiraGeoscience/simpeg#167.

[Copilot]

Pull request overview

Updates the production Python deployment workflow to derive the release tag from the GitHub ref context (instead of a manual input) and adds an early guard job to fail fast when a manual dispatch is not executed from a tag, aligning behavior with the referenced upstream change.

Changes:

• Remove the workflow_dispatchrelease-tag input and use ${{ github.ref_name }} as the tag source for manual runs.
• Add a validate-release-tag job that errors out when workflow_dispatch is run from a non-tag ref.
• Ensure both downstream publish jobs depend on the validation guard and use the computed release tag.

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