refactor: extract chapter title processing into domain/chapter_titles.py

- Extract simplify_heading_text, headings_equivalent, strip_duplicate_heading_line
- Extract normalize_caps_word, normalize_chapter_opening_caps
- Extract format_spoken_chapter_title
- Remove _HEADING_SANITIZE_RE, _HEADING_NUMBER_PREFIX_RE, _ACRONYM_ALLOWLIST, _ROMAN_NUMERAL_CHARS, _CAPS_WORD_RE from conversion_runner.py
- Add tests/test_chapter_titles.py with 31 tests
- All tests match old behavior

tests/test_chapter_titles.py

@@ -0,0 +1,144 @@
+"""Tests for domain/chapter_titles.py."""
+import sys
+import os
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..")))
+
+from abogen.domain.chapter_titles import (
+    simplify_heading_text,
+    headings_equivalent,
+    strip_duplicate_heading_line,
+    normalize_caps_word,
+    normalize_chapter_opening_caps,
+    format_spoken_chapter_title,
+)
+
+
+class TestSimplifyHeadingText:
+    def test_empty(self):
+        assert simplify_heading_text("") == ""
+
+    def test_none(self):
+        assert simplify_heading_text(None) == ""
+
+    def test_chapter_prefix_removed(self):
+        assert simplify_heading_text("Chapter 1") == "1"
+
+    def test_lowercase(self):
+        assert simplify_heading_text("Chapter 1: The Beginning") == "1thebeginning"
+
+    def test_strips_special_chars(self):
+        result = simplify_heading_text("Ch. 1")
+        assert "1" in result
+        assert "." not in result
+
+    def test_no_chapter_prefix(self):
+        result = simplify_heading_text("Part 2")
+        assert "part" in result
+
+
+class TestHeadingsEquivalent:
+    def test_exact_match(self):
+        assert headings_equivalent("Chapter 1", "Chapter 1")
+
+    def test_prefix_match(self):
+        assert headings_equivalent("Chapter 2", "Chapter 2: The Return")
+
+    def test_reverse_prefix(self):
+        assert headings_equivalent("Chapter 2: The Return", "Chapter 2")
+
+    def test_different_numbers(self):
+        assert not headings_equivalent("Chapter 1", "Chapter 2")
+
+    def test_empty(self):
+        assert not headings_equivalent("", "Chapter 1")
+
+    def test_long_containment(self):
+        assert headings_equivalent("Introduction", "Introduction to Everything")
+
+
+class TestStripDuplicateHeadingLine:
+    def test_removes_heading(self):
+        text = "Chapter 1\n\nSome text here"
+        result, removed = strip_duplicate_heading_line(text, "Chapter 1")
+        assert removed is True
+        assert "Chapter 1" not in result
+        assert "Some text here" in result
+
+    def test_no_heading(self):
+        text = "Just some text"
+        result, removed = strip_duplicate_heading_line(text, "Chapter 1")
+        assert removed is False
+        assert result == text
+
+    def test_empty_text(self):
+        result, removed = strip_duplicate_heading_line("", "Chapter 1")
+        assert removed is False
+
+    def test_strips_leading_empty_lines(self):
+        text = "Chapter 1\n\n\n\nText"
+        result, removed = strip_duplicate_heading_line(text, "Chapter 1")
+        assert removed is True
+        assert result.startswith("Text")
+
+
+class TestNormalizeCapsWord:
+    def test_acronym_kept(self):
+        assert normalize_caps_word("TTS") == "TTS"
+
+    def test_single_letter_kept(self):
+        assert normalize_caps_word("A") == "A"
+
+    def test_roman_numeral_kept(self):
+        assert normalize_caps_word("IV") == "IV"
+
+    def test_all_caps_converted(self):
+        result = normalize_caps_word("HELLO")
+        assert result == "Hello"
+
+    def test_with_hyphen(self):
+        result = normalize_caps_word("WELL-KNOWN")
+        assert result == "Well-Known"
+
+
+class TestNormalizeChapterOpeningCaps:
+    def test_all_caps_words(self):
+        text = "THIS IS A TEST"
+        result, changed = normalize_chapter_opening_caps(text)
+        assert changed is True
+        assert result == "This Is A Test"
+
+    def test_already_normal(self):
+        text = "This is normal"
+        result, changed = normalize_chapter_opening_caps(text)
+        assert changed is False
+
+    def test_empty(self):
+        result, changed = normalize_chapter_opening_caps("")
+        assert changed is False
+
+    def test_mixed(self):
+        text = "HELLO world"
+        result, changed = normalize_chapter_opening_caps(text)
+        assert changed is True
+
+
+class TestFormatSpokenChapterTitle:
+    def test_empty_no_prefix(self):
+        assert format_spoken_chapter_title("", 1, False) == ""
+
+    def test_empty_with_prefix(self):
+        assert format_spoken_chapter_title("", 1, True) == "Chapter 1"
+
+    def test_no_prefix_returns_base(self):
+        assert format_spoken_chapter_title("My Chapter", 1, False) == "My Chapter"
+
+    def test_already_has_chapter(self):
+        assert format_spoken_chapter_title("Chapter 5", 1, True) == "Chapter 5"
+
+    def test_number_prefix(self):
+        result = format_spoken_chapter_title("3. The End", 1, True)
+        assert result == "Chapter 3. The End"
+
+    def test_number_only(self):
+        result = format_spoken_chapter_title("7", 1, True)
+        assert result == "Chapter 7"