establish one canonical package documentation model

General MR

Summary

Key outcomes:

• All 45 integrated packages now declare their documentation in package-metadata.yaml.
• The package metadata generator now produces the package catalog, Core/Add-on indexes, and navigation.
• Added missing integration guides for BBCTL, Renovate, Headlamp, and Thanos.
• Replaced the manually maintained package matrix with the generated Integrated Packages catalog.
• Added validation for missing, malformed, or incorrectly categorized documentation in generate-package-schemas.jq.
• Documented the package-catalog workflow in CONTRIBUTING.md.
• Added catalog contract and validation coverage in the BATS tests.
• Added pre-commit and pre-push drift enforcement in lefthook.yaml.
• Preserved the old Add-on Renovate URL with a moved-page notice.

Additional changes:

• Reordered packages in json schema and package-metadata file based on alphabetical order

Relevant logs/screenshots

N/A

Linked Issue

Closes #3411 (closed)

Upgrade Notices

N/A