fix(arr): correct alass reference/subtitle argument order

Syncer::run passed [subtitle, video] where alass expects
<reference-file> <incorrect-sub-file>; every real invocation failed
before comparing timings, silently degrading to SyncState::NotRun.

crates/arr-subs/src/sync.rs

@@ -177,7 +177,9 @@ impl Syncer {
     async fn run(&self, video: &Path, subtitle: &Path, output: &Path) -> Result<()> {
         let mut command = Command::new(&self.binary);
         command
-            .args([subtitle, video])
+            // `alass <reference-file> <incorrect-sub-file> <output>`: the
+            // video is the reference, never the other way round.
+            .args([video, subtitle])
             .arg(output)
             .stdin(Stdio::null())
             .stdout(Stdio::null())
@@ -327,7 +329,7 @@ mod tests {
         "1\n00:00:01,000 --> 00:00:02,500\nol\u{e1}\n\n2\n00:00:03,000 --> 00:00:04,000\ntwo lines\nof text\n";
 
     /// Write an executable fake `alass`. Its body receives the three paths as
-    /// `$1` subtitle, `$2` video and `$3` output.
+    /// `$1` video, `$2` subtitle and `$3` output.
     async fn fake_binary(dir: &std::path::Path, body: &str) -> std::path::PathBuf {
         let path = dir.join("alass");
         let mut file = tokio::fs::File::create(&path)
@@ -372,7 +374,7 @@ mod tests {
     #[tokio::test]
     async fn an_unchanged_output_is_accepted_with_alass_text() {
         let dir = tempfile::tempdir().expect("test setup and fake binary succeed");
-        let binary = fake_binary(dir.path(), "cp \"$1\" \"$3\"\n").await;
+        let binary = fake_binary(dir.path(), "cp \"$2\" \"$3\"\n").await;
         let subtitle = write_subtitle(dir.path(), "in.srt", PLAIN).await;
 
         let outcome = Syncer::new()