style: apply cargo fmt across the crate (A20)

The repo never enforced rustfmt, so formatting had drifted broadly. This is a
single mechanical `cargo fmt` pass over the whole crate (no behavioral change;
lib suite green, 493 passed). Going forward fmt should be enforced (planned CI
fmt --check step). Part of the 0.6.1 hygiene pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/playlist.rs

@@ -49,9 +49,7 @@ pub fn parse_playlist(contents: &str, base_dir: &Path, kind: PlaylistKind) -> Ve
 
 fn playlist_entry_path(entry: &str, base_dir: &Path) -> Option<PathBuf> {
     let lower = entry.to_ascii_lowercase();
-    if lower.starts_with("http://")
-        || lower.starts_with("https://")
-        || lower.starts_with("ftp://")
+    if lower.starts_with("http://") || lower.starts_with("https://") || lower.starts_with("ftp://")
     {
         return None;
     }
@@ -107,7 +105,10 @@ File3=/var/audio/two.MP3
     #[test]
     fn playlist_kind_is_case_insensitive() {
         assert_eq!(playlist_kind(Path::new("mix.M3U")), Some(PlaylistKind::M3u));
-        assert_eq!(playlist_kind(Path::new("mix.m3u8")), Some(PlaylistKind::M3u));
+        assert_eq!(
+            playlist_kind(Path::new("mix.m3u8")),
+            Some(PlaylistKind::M3u)
+        );
         assert_eq!(playlist_kind(Path::new("mix.PLS")), Some(PlaylistKind::Pls));
         assert_eq!(playlist_kind(Path::new("mix.txt")), None);
     }