cli-core: catch-all field-render writeln! uses positional args instead of inline captures

[prasanna-anchorage]

Follow-up nit from #462 review.

In src/parser/cli-core/src/output.rs the new catch-all field-render arm does:

writeln!(writer, "{} {}: {}", prefix, field.label(), field.fallback_text())?;

prefix is a plain in-scope variable that could be captured inline, but this uses positional format arguments instead, against this repo's "use inline format strings" convention.

Fix: bind field.label()/field.fallback_text() to locals and use writeln!(writer, "{prefix} {label}: {text}")? (or similar) instead of positional args.