Make a Go net/rpc CLI non-interactive to drop a shell-parsing dependency

When porting an interactive Go client that read a line and split it with github.com/google/shlex into a scripted tool, take the arguments from os.Args instead: the invoking shell already handles quoting, so the dependency and the read loop disappear, and the tool becomes trivially callable over ssh (remote ... tool -E 'pattern'). Locate config relative to the binary with filepath.Join(filepath.Dir(os.Executable()), "..", "config.json") so it works from any cwd. Test the RPC end to end by registering the service on rpc.NewServer, listening on 127.0.0.1:0, and calling it through the real client function; for a grep wrapper cover match, no-match (exit 1, not an error) and bad pattern (exit 2).