[authorization] CLI helper `pnpm shefing-auth check <user> <collection>`

[tsemachh]

Plugin: authorization · Priority: P2 · Tracked by ROADMAP.md

Problem

Hard to debug effective permissions.

Proposed solution

CLI prints effective permissions for a user/collection pair.

Acceptance criteria

• Outputs allow/deny matrix.
• Reads same JWT logic as runtime.

How to claim

Comment on this issue (e.g. "I'd like to work on this") and a maintainer will assign it to you. Open a PR referencing this issue (Closes #<n>). Discuss design questions here or on the Payload Discord #plugins channel.