fix: resolve unused dependency lint issues

Remove genuinely stale deps (merlin, duration, digestif, eio_main,
dune-configurator, printbox, printbox-text, tls-eio, ocamlformat,
bytesrw-eio) and add missing library declarations to dune files
(eio+logs in ocaml-oci/src, logs in ocaml-git/lib+bin).

Keep js_of_ocaml in space-ground (needed for modes js) and add it
to implicit_deps in lint since it's a compiler, not a library.