Add a dedicated page listing all clients that support the Agent Skills
format. The `ClientShowcase` component renders the shared `clients` data
as a 2-column grid of cards, sorted alphabetically, with each card
showing the client logo, description, and links to setup instructions
and source code when available.
Add `"clients"` to the navigation in `docs.json`.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
