Add more validation and automation to the maintainer updates

[krook]

This PR updates the action that validates maintainer changes.

It makes sure that the required steps are done before we manually update records and merge changes.

It also highlights the additions, updates, and removals so staff doesn't have to sort that out manually from the diff.

A step further towards greater automation and self-service for maintainers 🎉

Example and test here: krook/copilot-testing#17

[Copilot]

Pull Request Overview

This PR introduces automated validation and change tracking for maintainer updates to the project-maintainers.csv file. It adds a new workflow to enforce PR checklist requirements and automatically generate change summaries.

• Adds a new GitHub Actions workflow (validate-maintainers.yml) that validates PR checklist completion and analyzes CSV changes
• Updates the CSV validation workflow to have a more descriptive name and consistent formatting
• Enhances the PR template with clearer instructions and a note directive

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
.github/workflows/validate-maintainers.yml	New workflow that validates PR checklist requirements, analyzes CSV changes, and posts automated comments with change summaries
.github/workflows/validate-csv.yml	Renamed workflow title and job name for clarity, standardized formatting
.github/pull_request_template.md	Updated template with clearer title, added GitHub note directive, and clarified email requirement for removals

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