feat: compare version model evaluations in the CLI

[leeclemnet]

What does this PR do?

Add roboflow eval compare --project … --version … to inspect the shared accuracy/latency comparison, including frontier membership and exclusions, as a table or full JSON. The command uses the public read-only endpoint and starts no evaluations.

Related Issue(s): Depends on platform comparison API.

Type of Change

• New feature (non-breaking change that adds functionality)

Testing

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in hard-to-understand areas
• My changes generate no new warnings or errors
• I have updated the documentation accordingly (if applicable)

Additional Context

Deploy the platform comparison endpoint before releasing the Python package. Workspace availability remains controlled by the platform feature flag.