Use the locally installed Zig binary to fetch documentation

[tristanpemble]

zig std serves the documentation server locally. by fetching the documentation from there, the MCP would use the version of Zig that is on the user's path, aka what is most relevant to the user.

I would go even further and suggest removing support of ziglang.org entirely to avoid the risk of bad actors downloading a 15MB tar from Zig's server every time they open their editor.

~ λ zig std --no-open-browser &
http://127.0.0.1:43695/
~ λ curl -O http://127.0.0.1:43695/sources.tar
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 14.0M    0 14.0M    0     0   621M      0 --:--:-- --:--:-- --:--:--  638M

[Afirium]

Hey, this is a great idea! I'll add support for fetching local docs and make that the recommended (default) way. Gonna keep ziglang.org around for now since it's cached anyway.