chore(repo): add a Milestone 6 access-control verification checklist

[alucero270]

chore(repo): add a Milestone 6 access-control verification checklist

Summary

Create the milestone-level verification checklist that must pass before Milestone 6 can be considered complete.

Scope

• Files: verification docs, likely docs/operations.md or a dedicated checklist section
• Components: authentication verification, authorization verification, retrieval access checks, required test commands

Acceptance Criteria

• the checklist covers authentication, source-scoped authorization, access-aware retrieval behavior, and required Milestone 6 test commands
• the checklist is runnable by another developer without hidden context
• the checklist clearly defines what must pass before the milestone is considered complete

Notes

• Milestone 6 is not complete until this checklist and the required tests are passing