fix(webui): voice.py imports from domain modules instead of conversion_runner

Replace private imports (_select_device, _to_float32, SAMPLE_RATE, SPLIT_PATTERN)
from abogen.webui.conversion_runner with proper domain imports:
- select_device from abogen.domain.device
- to_float32, SAMPLE_RATE from abogen.domain.audio_helpers
- SPLIT_PATTERN defined locally (r'\n+')

Also verifies preview.py already uses domain imports correctly.

7 new tests in tests/test_domain_imports.py enforce the architecture rule.

tests/test_domain_imports.py

@@ -0,0 +1,72 @@
+"""Tests that voice.py imports from domain modules, not from conversion_runner."""
+import pathlib
+
+
+def _read_source(module_file: str) -> str:
+    return pathlib.Path(module_file).read_text(encoding="utf-8")
+
+
+def test_voice_module_does_not_import_conversion_runner():
+    """voice.py must not import from conversion_runner (architecture rule)."""
+    import abogen.webui.routes.utils.voice as voice_mod
+
+    source_text = _read_source(voice_mod.__file__)
+
+    assert "from abogen.webui.conversion_runner import" not in source_text, (
+        "voice.py still imports from conversion_runner — must use domain modules"
+    )
+
+
+def test_voice_module_imports_select_device_from_domain():
+    """voice.py must import select_device from abogen.domain.device."""
+    import abogen.webui.routes.utils.voice as voice_mod
+
+    with open(voice_mod.__file__, "r", encoding="utf-8") as fh:
+        source_text = fh.read()
+
+    assert "from abogen.domain.device import" in source_text
+
+
+def test_voice_module_imports_to_float32_from_domain():
+    """voice.py must import to_float32 from abogen.domain.audio_helpers."""
+    import abogen.webui.routes.utils.voice as voice_mod
+
+    with open(voice_mod.__file__, "r", encoding="utf-8") as fh:
+        source_text = fh.read()
+
+    assert "from abogen.domain.audio_helpers import" in source_text
+
+
+def test_voice_module_has_sample_rate():
+    """voice.py must define SAMPLE_RATE = 24000."""
+    from abogen.webui.routes.utils.voice import SAMPLE_RATE
+
+    assert SAMPLE_RATE == 24000
+
+
+def test_voice_module_has_split_pattern():
+    """voice.py must define SPLIT_PATTERN."""
+    from abogen.webui.routes.utils.voice import SPLIT_PATTERN
+
+    assert isinstance(SPLIT_PATTERN, str)
+    assert len(SPLIT_PATTERN) > 0
+
+
+def test_preview_module_does_not_import_conversion_runner():
+    """preview.py must not import from conversion_runner."""
+    import abogen.webui.routes.utils.preview as preview_mod
+
+    with open(preview_mod.__file__, "r", encoding="utf-8") as fh:
+        source_text = fh.read()
+
+    assert "from abogen.webui.conversion_runner import" not in source_text
+
+
+def test_preview_module_imports_select_device_from_domain():
+    """preview.py must import select_device from abogen.domain.device."""
+    import abogen.webui.routes.utils.preview as preview_mod
+
+    with open(preview_mod.__file__, "r", encoding="utf-8") as fh:
+        source_text = fh.read()
+
+    assert "from abogen.domain.device import" in source_text