Install Python in update-bundle workflow

[mbg]

This was missed in #3257 and led to the failure in https://github.com/github/codeql-action/actions/runs/19100037542/job/54569501824

Risk assessment

For internal use only. Please select the risk level of this change:

• Low risk: Changes are fully under feature flags, or have been fully tested and validated in pre-production environments and are highly observable, or are documentation or test only.

Which use cases does this change impact?

CI only.

How did/will you validate this change?

• None - I am not validating these changes.

If something goes wrong after this change is released, what are the mitigation and rollback strategies?

N/A

How will you know if something goes wrong after this change is released?

CI failure.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Consider adding a changelog entry for this change.
• Confirm the readme and docs have been updated if necessary.

[Copilot]

Pull Request Overview

This PR refactors inline Python code in a GitHub Actions workflow into a separate script file. The changelog update logic that was previously embedded in the workflow YAML has been extracted to a standalone Python file.

• Extracts inline Python code from the workflow into a dedicated script file
• Adds Python setup step to ensure Python 3.12 is available for script execution
• Simplifies the workflow step by replacing inline code with a script invocation

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/update-bundle.yml	Adds Python setup step and replaces inline Python code with script invocation
.github/workflows/script/bundle_changelog.py	New script containing the extracted changelog update logic