fix: dev docs CI [skip tests]

[mkundu1]

Use the correct 26.1 image in the dev docs CI

[Copilot]

Pull Request Overview

This PR fixes the dev docs CI configuration by correcting the Docker image tag reference used across multiple workflow steps. The change replaces DOC_DEPLOYMENT_IMAGE_TAG with FLUENT_STABLE_IMAGE to ensure the correct 26.1 image is used.

Key Changes:

• Updated environment variable reference from DOC_DEPLOYMENT_IMAGE_TAG to FLUENT_STABLE_IMAGE across all workflow steps

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}