fix: add verification and playback safeguards

tests/test_audio_selection.py

@@ -0,0 +1,37 @@
+from fastapi.testclient import TestClient
+
+import stream_server
+
+
+def muted_entry(video):
+    return {
+        "video": video,
+        "mode": 1,
+        "vol": 0,
+        "pixel": False,
+        "cols": 200,
+        "rows": 0,
+    }
+
+
+def test_indexed_audio_does_not_use_global_current_index():
+    client = TestClient(stream_server.app)
+    stream_server.app.state.queue = [
+        muted_entry("missing-a.mp4"),
+        muted_entry("missing-b.mp4"),
+    ]
+    stream_server.app.state.current_index = 1
+
+    response = client.get("/audio/0")
+
+    assert response.status_code == 204
+
+
+def test_indexed_audio_rejects_out_of_range_index():
+    client = TestClient(stream_server.app)
+    stream_server.app.state.queue = [muted_entry("missing-a.mp4")]
+    stream_server.app.state.current_index = 0
+
+    response = client.get("/audio/99")
+
+    assert response.status_code == 404