Add mint score command to CLI reference

[mintlify]

Summary

• Documents the new mint score CLI command added in mintlify/mint#6993
• Adds usage, flags (--url, --format), and description to the CLI commands reference page

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Note

Low Risk
Documentation-only updates adding reference content for a new CLI command; no runtime or behavior changes.

Overview
Adds documentation for the new mint score CLI command, including usage, authentication requirement, --format flag, and the meaning of the reported readiness score.

Updates the CLI landing page to include a Check agent readiness callout referencing mint score <url>, and applies the same additions across EN/ES/FR/ZH docs.

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