Get Involved / Team Projects: old Team Projects link, misplaced handbook sentence, missing 2026 Contributor Day notes, outdated Advanced Administration text #467

Outdated text and links on Get Involved and Team Projects:

1. "several projects" goes to an old standalone page (get-involved.md#L5). It links https://make.wordpress.org/hosting/team-projects/, a separate page last modified in 2023 with older content ("The next step for this project is an audit"). It should link the handbook page: https://make.wordpress.org/hosting/handbook/get-involved/team-projects/. (Fix manifest generator dropping handbook hierarchy #442 edits the links on L7 but not this one.)
2. Handbook text under the tests heading (get-involved.md#L17-L19). Under "Improvements in the development of the Automated Hosting Tests", the sentence "The handbook is in the process of being audited and improved. You can see the progress and contribute through GitHub" links to phpunit-test-runner. It's a copy of the handbook sentence in team-projects.md#L28 and doesn't belong in the tests section.
3. Contributor Day Notes are missing two 2026 events (get-involved.md#L105-L115): the WordCamp Rajshahi 2026 Contributor Day summary and the WordCamp Europe 2026 Contributor Day post.
4. The Advanced Administration Handbook is described as not launched yet (team-projects.md#L79-L91): "This new documentation is proposed...", "Although we are still in a first step...", "If you want to help launch the Handbook as soon as possible... You can comment on the site itself". The handbook launched long ago at developer.wordpress.org/advanced-administration, and the site has no comment form. This text is copied from the 2023-01-15 status post. Suggested: describe it as live and point questions to #hosting on Slack or the GitHub issues.

AI Assisted Claude Code checked these pages against the live site and the team's blog. Each item was then confirmed.