fix(list-languages): clamp desired_width to avoid usize underflow at tiny --terminal-width

`get_languages` computed `desired_width = term_width - longest - separator.len()`.
When `--terminal-width` is smaller than the longest language name (e.g. 1), this
underflows `usize`: in overflow-checked builds it panics ("attempt to subtract with
overflow"), and in release it wraps to ~usize::MAX, silently disabling the extension
line-wrapping so `--terminal-width` is ignored for `--list-languages`.

Use `saturating_sub`, mirroring the fix applied to `print_snip` in #3804 (the snip
separator had the same `term_width - ...` underflow pattern). Output at normal widths
is unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/bin/bat/main.rs

@@ -152,7 +152,14 @@ pub fn get_languages(config: &Config, cache_dir: &Path) -> Result<String> {
         let comma_separator = ", ";
         let separator = " ";
         // Line-wrapping for the possible file extension overflow.
-        let desired_width = config.term_width - longest - separator.len();
+        // Clamp instead of subtracting: a tiny `--terminal-width` (smaller than the
+        // longest language name) would otherwise underflow `usize` and wrap to a huge
+        // value, silently disabling wrapping (and panicking in debug/overflow-checked
+        // builds). Mirrors the `saturating_sub` fix applied to `print_snip` in #3804.
+        let desired_width = config
+            .term_width
+            .saturating_sub(longest)
+            .saturating_sub(separator.len());
 
         let style = if config.colored_output {
             Green.normal()