Function validate_dynamic_lexer_callbacks 

pub fn validate_dynamic_lexer_callbacks(
    resolved: ResolvedLexer,
    has_lexer_callbacks: bool,
) -> Result<(), FrontendError>

The dynamic/dynamic_complete lexer forbids lexer_callbacks — Lark raises GrammarError("Earley's dynamic lexer doesn't support lexer_callbacks.") at Earley-parser construction, after resolve_lexer. Callers pass the resolved lexer; the check is a no-op for any non-dynamic lexer.