Function parse_command_in_ctx 

pub fn parse_command_in_ctx(
    ctx: &Context,
    surface: &Surface,
    input: &str,
) -> Result<Command, ParseError>

Parse ONE command with the kernel CONTEXT available, and require it to be the whole input.

parse_command_prefix_in_ctx plus “and nothing followed” — the context-aware counterpart of parse_command, and what Repl::execute should read its command through.