refactor: wire up domain/chapter_overrides.py and domain/metadata_merge.py

- Update chapter_overrides.py to return tuple matching original signature
- Import apply_chapter_overrides and merge_metadata from domain modules
- Remove old function bodies from conversion_runner.py
- Add tests/test_chapter_merge_normalize.py (19 tests)
- conversion_runner.py: 1677 → 1574 lines
- All tests pass

tests/test_chapter_merge_normalize.py

@@ -0,0 +1,167 @@
+"""Tests for chapter_overrides, merge_metadata, normalize_for_pipeline.
+
+Tests import from domain modules (new location).
+"""
+
+from __future__ import annotations
+
+import pytest
+from abogen.text_extractor import ExtractedChapter
+
+
+# ---------------------------------------------------------------------------
+# apply_chapter_overrides
+# ---------------------------------------------------------------------------
+
+
+class TestApplyChapterOverrides:
+    """apply_chapter_overrides applies chapter overrides to extracted chapters."""
+
+    def test_empty_overrides(self):
+        from abogen.domain.chapter_overrides import apply_chapter_overrides
+
+        result, updates, diags = apply_chapter_overrides([], [])
+        assert result == []
+        assert updates == {}
+        assert diags == []
+
+    def test_basic_override_by_index(self):
+        from abogen.domain.chapter_overrides import apply_chapter_overrides
+
+        chapters = [ExtractedChapter(title="Ch1", text="original")]
+        overrides = [{"index": 0, "title": "New Title", "text": "new text"}]
+        result, updates, diags = apply_chapter_overrides(chapters, overrides)
+        assert len(result) == 1
+        assert result[0].title == "New Title"
+        assert result[0].text == "new text"
+
+    def test_override_by_source_title(self):
+        from abogen.domain.chapter_overrides import apply_chapter_overrides
+
+        chapters = [ExtractedChapter(title="Ch1", text="text1")]
+        overrides = [{"source_title": "Ch1", "title": "Renamed"}]
+        result, _, _ = apply_chapter_overrides(chapters, overrides)
+        assert result[0].title == "Renamed"
+
+    def test_disabled_override_skipped(self):
+        from abogen.domain.chapter_overrides import apply_chapter_overrides
+
+        chapters = [ExtractedChapter(title="Ch1", text="text1")]
+        overrides = [{"index": 0, "enabled": False}]
+        result, _, _ = apply_chapter_overrides(chapters, overrides)
+        assert len(result) == 0
+
+    def test_metadata_updates_collected(self):
+        from abogen.domain.chapter_overrides import apply_chapter_overrides
+
+        chapters = [ExtractedChapter(title="Ch1", text="text1")]
+        overrides = [{"index": 0, "metadata": {"album": "New Album"}}]
+        _, updates, _ = apply_chapter_overrides(chapters, overrides)
+        assert updates["album"] == "New Album"
+
+    def test_no_matching_chapter_diagnostic(self):
+        from abogen.domain.chapter_overrides import apply_chapter_overrides
+
+        overrides = [{"index": 99, "title": "X"}]
+        _, _, diags = apply_chapter_overrides([], overrides)
+        assert len(diags) == 1
+        assert "Skipped" in diags[0]
+
+    def test_non_dict_override_skipped(self):
+        from abogen.domain.chapter_overrides import apply_chapter_overrides
+
+        _, _, diags = apply_chapter_overrides([], ["bad"])
+        assert len(diags) == 1
+
+    def test_text_from_base_when_not_provided(self):
+        from abogen.domain.chapter_overrides import apply_chapter_overrides
+
+        chapters = [ExtractedChapter(title="Ch1", text="original text")]
+        overrides = [{"index": 0, "title": "New Title"}]
+        result, _, _ = apply_chapter_overrides(chapters, overrides)
+        assert result[0].text == "original text"
+
+    def test_default_title_when_no_base(self):
+        from abogen.domain.chapter_overrides import apply_chapter_overrides
+
+        overrides = [{"text": "some text"}]
+        result, _, _ = apply_chapter_overrides([], overrides)
+        assert result[0].title == "Chapter 1"
+
+
+# ---------------------------------------------------------------------------
+# merge_metadata
+# ---------------------------------------------------------------------------
+
+
+class TestMergeMetadata:
+    """merge_metadata merges extracted metadata with overrides."""
+
+    def test_both_empty(self):
+        from abogen.domain.metadata_merge import merge_metadata
+
+        assert merge_metadata({}, {}) == {}
+
+    def test_only_extracted(self):
+        from abogen.domain.metadata_merge import merge_metadata
+
+        result = merge_metadata({"album": "Book"}, {})
+        assert result == {"album": "Book"}
+
+    def test_only_overrides(self):
+        from abogen.domain.metadata_merge import merge_metadata
+
+        result = merge_metadata(None, {"album": "Override"})
+        assert result == {"album": "Override"}
+
+    def test_override_wins(self):
+        from abogen.domain.metadata_merge import merge_metadata
+
+        result = merge_metadata({"album": "Old"}, {"album": "New"})
+        assert result == {"album": "New"}
+
+    def test_none_value_deletes_key(self):
+        from abogen.domain.metadata_merge import merge_metadata
+
+        result = merge_metadata({"album": "Book"}, {"album": None})
+        assert "album" not in result
+
+    def test_none_values_in_extracted_skipped(self):
+        from abogen.domain.metadata_merge import merge_metadata
+
+        result = merge_metadata({"album": None, "artist": "X"}, {})
+        assert result == {"artist": "X"}
+
+    def test_numeric_values_stringified(self):
+        from abogen.domain.metadata_merge import merge_metadata
+
+        result = merge_metadata({"track": 1}, {})
+        assert result["track"] == "1"
+
+
+# ---------------------------------------------------------------------------
+# normalize_for_pipeline (thin wrapper)
+# ---------------------------------------------------------------------------
+
+
+class TestNormalizeForPipeline:
+    """normalize_for_pipeline normalizes text with runtime settings."""
+
+    def test_basic_normalize(self):
+        from abogen.webui.conversion_runner import _normalize_for_pipeline
+
+        result = _normalize_for_pipeline("Hello   World")
+        assert isinstance(result, str)
+        assert len(result) > 0
+
+    def test_empty_string(self):
+        from abogen.webui.conversion_runner import _normalize_for_pipeline
+
+        result = _normalize_for_pipeline("")
+        assert result == ""
+
+    def test_with_overrides(self):
+        from abogen.webui.conversion_runner import _normalize_for_pipeline
+
+        result = _normalize_for_pipeline("test", normalization_overrides={"number_format": "words"})
+        assert isinstance(result, str)