Function load_command_input 

pub fn load_command_input(
    args: &[String],
    stdin: impl Read,
) -> Result<Value, LoadError>

Load a command Value from positional args or stdin.

Called after extension dispatch fails (no argv match). Remaining cases:

• .json → read file and parse JSON
• otherwise → parse the argument as inline JSON

.md shorthand is handled by the shipped markdown-suffix registry in main before this function runs.

Errors

Returns LoadError::Usage for invalid argv shapes or empty stdin, LoadError::Parse for invalid JSON, and LoadError::Io for read failures.