Function parse_send_tokens 

pub fn parse_send_tokens(
    tokens: &[String],
) -> Result<InjectionCommand, AppError>

Parse a semantic omni send token list into an InjectionCommand.

Grammar (first token is the kind):

• text <words...> — remaining tokens joined with single spaces
• key <name> — a single semantic key name
• combo <spec> — a single ComboEngine string, e.g. ctrl,a,g
• scroll <n> — a signed integer line count

Errors

Returns AppError::validation for an unknown/missing kind, a missing value, or a non-integer scroll amount.