Add VIA Network MCP server to the extensions registry

[richardjhobbs]

Summary

Adds VIA Network as a remote (streamable HTTP) extension.

VIA is an agentic commerce network. Sellers expose a Sales Agent over MCP that knows their own catalogue, stock and pricing; buyers can post a brief and collect offers. The network endpoint at https://app.getvia.xyz/mcp is a gateway, so goose talks to one URL and the transaction tools forward to the seller or buyer that owns the record.

No API key or environment variables. Discovery is free. Purchases return an x402 payment requirement that the buyer's own wallet signs, and settlement is posted back to VIA in USDC on Base.

Two files, matching the pattern used by #9861:

• documentation/static/servers.json: one new entry, via-network
• documentation/docs/mcp/via-network-mcp.md: tutorial page with Desktop and CLI install tabs

Testing

• https://app.getvia.xyz/mcp verified live over streamable HTTP: tools/list returns 29 tools (list_sellers, find_seller, get_product, ask_sales_agent, request_quote, counter_quote, negotiate, buy_product, confirm_purchase, get_download_links, register_store among them).
• Modified servers.json parses cleanly and the rest of the file is untouched.
• The server is also listed in the official MCP Registry as xyz.getvia.app/via-network.

Related Issues

None.

Screenshots/Demos (for UX changes)

Not applicable, docs and registry entry only.

[alexhancock]

🤖 Thanks so much for this contribution!

We're retiring goose's own MCP server registry in favor of the official, community-governed MCP registry and its server.json format. Effective immediately we're no longer accepting new server contributions (or edits) to our registry, so I'm closing this PR.

Full context here: #10830

We'd love to see your extension published to the official registry instead — that's now the path for discoverability across the ecosystem. Thanks again for your interest in goose! 🙏