fix(audio): accept immersive channel layouts like 5.1.4

parse_channels rejected a three-figure layout, so a remote download crashed rebuilding the track from JSON. Add channel_total so --channels can compare either form.

tests/tracks/test_audio_channel_layouts.py

@@ -0,0 +1,46 @@
+"""Channel values that no float can hold.
+
+An immersive layout names its height channels in a third figure, e.g. 5.1.4. A service
+assigning that straight onto a track keeps it out of validation, but a remote download
+sends the track as JSON and rebuilds it through Audio(), which parses the value.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from unshackle.core.tracks import Audio
+
+
+@pytest.mark.parametrize("layout", ["5.1.4", "7.1.2", "9.1.6"])
+def test_an_immersive_layout_survives_construction(layout: str) -> None:
+    assert Audio(id_="a1", url="https://example.test/a", language="en", channels=layout).channels == layout
+
+
+@pytest.mark.parametrize(
+    ("value", "expected"),
+    [("5.1", 5.1), ("2ch", 2.0), ("2", 2.0), ("2.0", 2.0), ("A000", 2.0), ("F801", 5.1), (6, 6.0)],
+)
+def test_existing_channel_forms_are_unchanged(value: object, expected: float) -> None:
+    assert Audio.parse_channels(value) == expected
+
+
+@pytest.mark.parametrize("value", ["stereo", "5.1.4.2", "", "..", "5.x.4"])
+def test_a_value_that_is_no_layout_still_raises(value: str) -> None:
+    with pytest.raises(NotImplementedError):
+        Audio.parse_channels(value)
+
+
+def test_an_immersive_layout_round_trips_as_a_dict() -> None:
+    """A remote download rebuilds every track from the dict the server sent."""
+    track = Audio(id_="a1", url="https://example.test/a", language="en", channels="5.1.4", bitrate=448000)
+    assert Audio.from_dict(track.to_dict()).channels == "5.1.4"
+
+
+@pytest.mark.parametrize(
+    ("channels", "total"),
+    [("5.1.4", 10.0), ("7.1.2", 10.0), (5.1, 5.1), (6.0, 6.0), ("2.0", 2.0)],
+)
+def test_channel_total_compares_both_forms(channels: object, total: float) -> None:
+    """--channels rounds the sub channel up, so both forms have to reach that arithmetic."""
+    assert Audio.channel_total(channels) == total