fix: trailing newline in footer_ui.rs (cargo fmt)

Author: donglovejava

crates/tui/src/tui/footer_ui.rs

@@ -885,4 +885,4 @@ pub(crate) fn format_context_budget(used: i64, max: u32) -> String {
 #[cfg(test)]
 pub(crate) fn spans_width(spans: &[Span<'_>]) -> usize {
     spans.iter().map(|span| span.content.width()).sum()
-}
+}