refactor(webui): replace inline get_pipeline/resolve_voice_target closures with domain modules

- Replace get_pipeline() closure with PipelinePool from domain/pipeline_factory
- Replace resolve_voice_target() closure with domain function from voice_utils
- Remove dead _load_pipeline() function and unused is_plugin_registered import
- Add 33 tests for resolve_voice_target and PipelinePool
- Add 10 regression tests verifying domain extraction preserves behavior
- 1131 tests pass (+61 new)

tests/test_domain_voice_utils.py

@@ -0,0 +1,195 @@
+from __future__ import annotations
+
+from unittest.mock import patch
+
+from abogen.domain.voice_utils import (
+    coerce_truthy,
+    formula_from_kokoro_entry,
+    infer_provider_from_spec,
+    resolve_voice_target,
+    split_speaker_reference,
+    supertonic_voice_from_spec,
+)
+
+
+class TestSplitSpeakerReference:
+    def test_speaker_prefix(self):
+        assert split_speaker_reference("speaker:af_sarah") == ("af_sarah", "speaker:af_sarah")
+
+    def test_profile_prefix(self):
+        assert split_speaker_reference("profile:custom") == ("custom", "profile:custom")
+
+    def test_no_prefix(self):
+        assert split_speaker_reference("af_sarah") == (None, "af_sarah")
+
+    def test_empty(self):
+        assert split_speaker_reference("") == (None, "")
+
+    def test_none(self):
+        assert split_speaker_reference(None) == (None, "")
+
+    def test_unknown_prefix(self):
+        assert split_speaker_reference("unknown:name") == (None, "unknown:name")
+
+    def test_empty_name_after_colon(self):
+        assert split_speaker_reference("speaker:") == (None, "speaker:")
+
+
+class TestSupertonicVoiceFromSpec:
+    def test_uppercase_passthrough(self):
+        assert supertonic_voice_from_spec("M1", "M1") == "M1"
+
+    def test_lowercase_converted(self):
+        assert supertonic_voice_from_spec("m1", "M1") == "M1"
+
+    def test_empty_spec_uses_fallback(self):
+        assert supertonic_voice_from_spec("", "F1") == "F1"
+
+    def test_formula_spec_uses_fallback(self):
+        assert supertonic_voice_from_spec("af_sarah*0.5+bf_emma*0.5", "M1") == "M1"
+
+    def test_empty_both_gives_default(self):
+        assert supertonic_voice_from_spec("", "") == "M1"
+
+
+class TestFormulaFromKokoroEntry:
+    def test_single_voice(self):
+        entry = {"voices": [["af_sarah", 1.0]]}
+        result = formula_from_kokoro_entry(entry)
+        assert "af_sarah" in result
+        assert "1.000000" in result
+
+    def test_weighted_mix(self):
+        entry = {"voices": [["af_sarah", 0.6], ["bf_emma", 0.4]]}
+        result = formula_from_kokoro_entry(entry)
+        assert "af_sarah" in result
+        assert "bf_emma" in result
+        assert "+" in result
+
+    def test_empty_voices(self):
+        assert formula_from_kokoro_entry({"voices": []}) == ""
+
+    def test_missing_voices_key(self):
+        assert formula_from_kokoro_entry({}) == ""
+
+    def test_invalid_entries_filtered(self):
+        entry = {"voices": [["af_sarah", "bad"], ["bf_emma", 0.5]]}
+        result = formula_from_kokoro_entry(entry)
+        assert "bf_emma" in result
+        assert "af_sarah" not in result
+
+
+class TestCoerceTruthy:
+    def test_bool_passthrough(self):
+        assert coerce_truthy(True) is True
+        assert coerce_truthy(False) is False
+
+    def test_string_true(self):
+        assert coerce_truthy("yes") is True
+        assert coerce_truthy("1") is True
+
+    def test_string_false(self):
+        assert coerce_truthy("false") is False
+        assert coerce_truthy("0") is False
+        assert coerce_truthy("") is False
+
+    def test_none_default(self):
+        assert coerce_truthy(None) is True
+        assert coerce_truthy(None, False) is False
+
+    def test_int(self):
+        assert coerce_truthy(1) is True
+        assert coerce_truthy(0) is False
+
+
+class TestInferProviderFromSpec:
+    @patch("abogen.domain.voice_utils.get_voices", return_value=["af_sarah", "bf_emma"])
+    def test_known_kokoro_voice(self, _mock):
+        assert infer_provider_from_spec("af_sarah") == "kokoro"
+
+    @patch("abogen.domain.voice_utils.get_voices", return_value=["af_sarah"])
+    def test_uppercase_supertonic(self, _mock):
+        assert infer_provider_from_spec("M1") == "supertonic"
+
+    @patch("abogen.domain.voice_utils.get_voices", return_value=["af_sarah"])
+    def test_formula_kokoro(self, _mock):
+        assert infer_provider_from_spec("af_sarah*0.5+bf_emma*0.5") == "kokoro"
+
+    @patch("abogen.domain.voice_utils.get_voices", return_value=["af_sarah"])
+    def test_empty_fallback(self, _mock):
+        assert infer_provider_from_spec("", "kokoro") == "kokoro"
+
+    @patch("abogen.domain.voice_utils.get_voices", return_value=["af_sarah"])
+    def test_unknown_falls_back(self, _mock):
+        assert infer_provider_from_spec("unknown_xyz", "supertonic") == "supertonic"
+
+
+class TestResolveVoiceTarget:
+    def test_empty_spec_kokoro_default(self):
+        provider, spec, speed, steps = resolve_voice_target(
+            "", {}, job_voice="af_sarah", job_tts_provider="kokoro",
+        )
+        assert provider == "kokoro"
+        assert spec == ""
+
+    def test_speaker_profile_kokoro(self):
+        profiles = {
+            "narrator": {
+                "provider": "kokoro",
+                "voices": [["af_sarah", 0.7], ["bf_emma", 0.3]],
+            },
+        }
+        provider, spec, speed, steps = resolve_voice_target(
+            "speaker:narrator", profiles,
+        )
+        assert provider == "kokoro"
+        assert "af_sarah" in spec
+        assert speed is None
+        assert steps is None
+
+    def test_speaker_profile_supertonic(self):
+        profiles = {
+            "narrator": {
+                "provider": "supertonic",
+                "voice": "F1",
+                "speed": 1.2,
+                "total_steps": 10,
+            },
+        }
+        provider, spec, speed, steps = resolve_voice_target(
+            "speaker:narrator", profiles,
+            job_voice="M1", job_speed=1.0, job_supertonic_total_steps=5,
+        )
+        assert provider == "supertonic"
+        assert spec == "F1"
+        assert speed == 1.2
+        assert steps == 10
+
+    @patch("abogen.domain.voice_utils.get_voices", return_value=["af_sarah"])
+    def test_direct_supertonic_spec(self, _mock):
+        provider, spec, speed, steps = resolve_voice_target(
+            "M1", {},
+            job_voice="M1",
+        )
+        assert provider == "supertonic"
+        assert spec == "M1"
+
+    @patch("abogen.domain.voice_utils.get_voices", return_value=["af_sarah"])
+    def test_direct_kokoro_spec(self, _mock):
+        provider, spec, speed, steps = resolve_voice_target(
+            "af_sarah", {},
+            job_tts_provider="kokoro",
+        )
+        assert provider == "kokoro"
+        assert spec == "af_sarah"
+
+    def test_profile_missing_provider_defaults_kokoro(self):
+        profiles = {
+            "narrator": {
+                "voices": [["af_sarah", 1.0]],
+            },
+        }
+        provider, spec, speed, steps = resolve_voice_target(
+            "speaker:narrator", profiles,
+        )
+        assert provider == "kokoro"