ANU-20: Repository-change CLI and canonical workflow

ANU-20 implements the Product Main foundation for the approved ANU-19 repository-scoped change workflow. It introduces guarded standalone repository-change intake and completion, creates the canonical implicit skill contract, preserves the existing Product Main child workflow, and removes the issue-free maintenance workflow.

Review artifacts

• Implementation Plan defines the proposed command, schema, issue-kind, delivery, skill, documentation, and verification changes.
• Implementation Log records the approved implementation as it proceeds.
• Completion Report will map the delivered result to acceptance and verification evidence.

The exact current Implementation Plan was approved by Girish on 2026-07-28 at 12:12 UTC.