Create pf-track-component-usage skill

[patternfly-jira-sync]

Scans a codebase and reports which PF components, props, and variants are actually in use. Useful for migration planning and impact analysis.

AC:

• Skill exists in migration plugin

• Produces a usage inventory from a target codebase

• Covers components, props, and variant usage

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Jira Issue: PF-4174