S174: SV-C1 safaa positional args, SV-C2 tier chunked, SV-C3 indent, SV-C4 stale files

app.py

@@ -332,10 +332,13 @@ def _run_engine(job_id):
                 job["out_path"].replace(".mp3", "_safaa_tmp.wav")
                 if _is_safaa else job["out_path"]
             )
-            cmd = ["python3", str(script),
-                   "-i", job["in_path"], "-o", _o_path]
-            if not _is_safaa:
-                cmd += ["--iterations", "3"]
+            # S174-SV-C1: safaa uses positional args (input output), not -i/-o flags
+            if _is_safaa:
+                cmd = ["python3", str(script), job["in_path"], _o_path]
+            else:
+                cmd = ["python3", str(script),
+                       "-i", job["in_path"], "-o", _o_path,
+                       "--iterations", "3"]
                 for rf in ref_files[:3]: cmd += ["--ref", str(rf)]
             proc = subprocess.Popen(cmd, stdout=subprocess.PIPE,
                                     stderr=subprocess.STDOUT, text=True)