[dzucconi]

Updates the MCP server to the current Are.na API contract and fixes custom tools that were still reading older response fields.

• Refresh the OpenAPI spec and generated types, including the updated rate-limit information.
• Fix search-and-connect to recognize results by type, and channel digests to read current descriptions and connection activity.
• Preserve metadata value types, null deletions, and numeric bounds in generated input validation.
• Return valid MCP text for successful responses with no body.
• Add offline regeneration and regression tests through the MCP HTTP transport.