CLI: Add model detail view

[cardmagic]

Summary

Add the ability to view detailed information about a specific model in a registry.

Motivation

Users should be able to see full metadata about a model before downloading it, including description, author, version, categories, and size.

Proposed Syntax

# View model details from default registry
classifier models spam-filter
# => Name: spam-filter
# => Description: Email spam detection trained on SpamAssassin corpus
# => Type: bayes
# => Categories: spam, ham
# => Version: 1.0.0
# => Author: cardmagic
# => Size: 245KB

# View model details from custom registry
classifier models @user/repo:sentiment
# => Name: sentiment
# => Description: Positive/negative sentiment analysis
# => ...

Implementation Notes

• Detect when argument is a model name vs registry path
• Fetch and display all available metadata from models.json
• Could also support --local to show details of cached models

Related

• Part of Add CLI executable for training and classification #119 CLI specification
• Follow-up from Add CLI executable with model registry support #127