Add Spanish, Italian and Russian; dropdown order and language file tests

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/gfx.rs

@@ -2189,7 +2189,15 @@ mod font_tests {
         let (_, map) = load_font();
         let question = font_src(&map, '?');
         let mut missing = std::collections::BTreeSet::new();
-        for file in [include_str!("../lang/en.lang"), include_str!("../lang/de.lang")] {
+        // every language file in lang/
+        let files: Vec<String> = std::fs::read_dir("lang")
+            .expect("lang directory")
+            .filter_map(|e| e.ok())
+            .filter(|e| e.path().extension().map_or(false, |x| x == "lang"))
+            .map(|e| std::fs::read_to_string(e.path()).expect("language file"))
+            .collect();
+        assert!(files.len() >= 2);
+        for file in &files {
             for ch in file.chars().filter(|c| !c.is_control() && *c != ' ') {
                 if ch != '?' && font_src(&map, ch) == question {
                     missing.insert(ch);