ANU-21: Bento Repository-change Workflow

This change adopts the Product Main-owned repository-change workflow in the Anuva Bento downstream without changing Bento product behavior or upstream source.

• Implementation Plan
• Implementation Log
• Completion Report
• Linear: ANU-21
• Product Main source: docs/changes/2026-07-28-anu-19-repository-change-workflow/index.md
• Product Main review preview: https://main1.girishd.com/changes/2026-07-28-anu-19-repository-change-workflow/
• Draft PR: Shoonya-Game-Technologies/anuva-bento#7
• Status: implementation and verification complete; In Review on the linked draft PR