Add 404.directory remote MCP server

[MM-sheng]

Adds the hosted remote MCP server https://404.directory/mcp.

• understand_webpage: structured webpage semantics
• verify_web: independent HTTP/HTTPS/content verification
• Official Registry: https://registry.modelcontextprotocol.io/v0.1/servers/io.github.MM-sheng%2F404-directory/versions/latest
• Both tools tested with MCP initialize, tools/list, and tools/call.

[MM-sheng]

Update: the endpoint is live and revalidated on 2026-08-19.

• GET https://404.directory/.well-known/mcp.json returns HTTP 200 and advertises both tools.
• MCP initialize and tools/list succeed against https://404.directory/mcp (protocol 2025-06-18, server 0.4.4).
• The endpoint is also registered in the open mcpub directory.

No credentials are required for these read-only tools.

[MM-sheng]

Superseded by #14, which contains the current 12-tool hosted MCP metadata and verification. Closing the older duplicate to keep one review target.