OK, one more option (embarrassingly the most obvious one...):
5. Process the metadata (as S-expressions) already on the
documentation web-server and directly communicate with that server
from the editor.
- Scheme-side implementation required only for the one
Scheme we anyway use to build the server.
- No local Scheme client (server or REPL) required.
- No access to additional Scheme specific introspection and
documentation features; we can only present what we can
define as metadata.
- Performance will be worse than for the local client;
whether this is noticeable for the highly interactive
features (hovering, Emacs-eldoc) needs to be checked.
- I'm not sure whether all interesting features incl. those
defined by LSP can be handled by HTTP and I might oversee a
limitation that we have in the HTTP-case that we would not
have in the local-socket case.