Add support for resource links

Currently, Claude seems unable to work with resource links returned from tools:

> get evcc docs

[DEBUG] MCP server "evcc": Tool call succeeded: {"content":[{"name":"evcc-docs","uri":"https://docs.evcc.io","description":"evcc documentation","mimeType":"text/html","type":"resource_link"}]}

...

⏺ The evcc docs tool ran successfully but returned no output. The documentation for evcc is typically available at https://docs.evcc.io, and based on
  the project structure in CLAUDE.md, you can also generate docs locally using make docs command.

It would be nice to actually work with these remote resources.