feat(docs): add collection description tooltips to Docusaurus collections page

[WilliamBerryiii]

Summary

The collections overview page at docs/getting-started/collections.md displays a table of available collections with artifact counts and marketplace links. Each collection also has a *.collection.md file containing a richer description of its purpose and contents.

Proposal

Add hover tooltips (or an expandable details row) to the Docusaurus collections page that surface the summary from each collections/*.collection.md file. This would let users understand what each collection offers without navigating away from the overview table.

Suggested Approach

• Parse the first paragraph or frontmatter description from each *.collection.md file
• Render as a tooltip on hover over the collection name, or as an expandable accordion row beneath each table entry
• Consider using a Docusaurus MDX component or custom React component similar to the existing Icons/index.tsx pattern

Context

This idea came out of PR #950 where the collections overview table was enhanced with per-artifact counts and marketplace links. The table provides a quick reference but the one-line descriptions can only convey so much.

Acceptance Criteria

• Collection descriptions are accessible from the overview page without navigating to individual collection docs
• Descriptions stay in sync with *.collection.md source files
• Implementation follows existing Docusaurus component conventions