check-versions

Verify version consistency across plugin.json and marketplace.json for all plugins. Use when (1) before creating a pull request or release to ensure metadata consistency, (2) after manually editing version numbers in either plugin.json or marketplace.json, (3) repository health verification or preflight checks are requested, (4) after using bump-version to confirm both files were updated correctly, (5) during debugging if plugins aren't appearing correctly in the marketplace, (6) as part of comprehensive validation alongside check-skill-counts and check-changelogs.