refactor: heading transforms + dedup moved to shared layer

- conversion_planner.py: caps normalization in _build_chapters()
- conversion_executor.py: heading dedup + state machine via headings_equivalent()
- Fixed seg_start_time → chapter_body_start bug in executor
- Removed getattr fallback defaults in both adapters
- Added 4 tests for caps normalization and heading dedup
- Updated ARCHITECTURE_REFACTOR_PLAN.md with deferred WebUI cleanup

abogen/application/conversion_executor.py

@@ -32,6 +32,10 @@ from abogen.domain.conversion_engine import (
 )
 from abogen.domain.enums import OutputFormat, SubtitleMode
 from abogen.domain.normalization import TTSContext
+from abogen.domain.chapter_titles import (
+    apply_chapter_text_transforms,
+    headings_equivalent as _headings_equivalent,
+)
 from abogen.domain.output_paths import sanitize_filename_for_chapter
 from abogen.infrastructure.subtitle_writer import make_subtitle_writer
 
@@ -249,6 +253,7 @@ def execute_conversion(
                     )
 
             # Process heading
+            heading_text = ""
             if chapter.title:
                 heading_text = _format_heading(chapter.title, chapter_idx, request)
                 if heading_text:
@@ -269,11 +274,37 @@ def execute_conversion(
                             stats=stats,
                         )
 
+            # Heading dedup: check if first line of body matches heading
+            pending_heading_strip = False
+            if heading_text and chapter.body_text:
+                first_line = next(
+                    (line.strip() for line in chapter.body_text.splitlines() if line.strip()),
+                    "",
+                )
+                if first_line and _headings_equivalent(first_line, heading_text):
+                    pending_heading_strip = True
+
             # Process body segments
             chapter_chunk_markers: List[Dict[str, Any]] = []
+            chapter_body_start = stats.current_time
             for seg_idx, segment in enumerate(chapter.segments):
                 check_cancelled()
 
+                # Apply heading dedup to first segment (consume-once)
+                seg_text = segment.text
+                if pending_heading_strip and seg_text.strip():
+                    seg_text, heading_removed, _ = apply_chapter_text_transforms(
+                        seg_text,
+                        heading_text=heading_text,
+                        raw_title=chapter.title,
+                        strip_heading=True,
+                        normalize_caps=False,
+                    )
+                    if heading_removed:
+                        pending_heading_strip = False
+                    if not seg_text.strip():
+                        continue
+
                 # Resolve segment voice (may differ from chapter voice)
                 if segment.voice_spec != chapter.voice_spec:
                     seg_provider, seg_voice, seg_speed, seg_steps = _resolve_voice(
@@ -288,7 +319,7 @@ def execute_conversion(
 
                 seg_start_time = stats.current_time
                 local_segments, accumulated_tokens = synthesize_text(
-                    text=segment.text,
+                    text=seg_text,
                     params=synth,
                     backend=seg_backend,
                     voice=seg_voice,
@@ -355,7 +386,7 @@ def execute_conversion(
             result.chapter_markers.append({
                 "chapter_index": chapter_idx - 1,
                 "title": chapter.title,
-                "start": stats.current_time - (stats.current_time - seg_start_time) if chapter.segments else stats.current_time,
+                "start": chapter_body_start,
                 "end": stats.current_time,
             })
 

abogen/application/conversion_planner.py

@@ -210,9 +210,15 @@ def _build_chapters(
     selected_chapters: List[Tuple[str, str, str]], request: ConversionRequest
 ) -> List[ChapterPlan]:
     """Build ChapterPlan with SegmentPlan for each chapter."""
+    from abogen.domain.chapter_titles import normalize_chapter_opening_caps
+
     chapters = []
 
     for idx, (title, body_text, default_voice) in enumerate(selected_chapters, 1):
+        # Apply caps normalization to body text if enabled
+        if request.normalize_chapter_opening_caps and body_text:
+            body_text, _ = normalize_chapter_opening_caps(body_text)
+
         # Build segments for this chapter (idx is 1-based, chunks use 0-based)
         segments = _build_segments(body_text, default_voice, request, chapter_index=idx - 1)
 

abogen/pyqt/conversion_adapter.py

@@ -112,7 +112,7 @@ def build_conversion_request_from_thread(thread: Any) -> ConversionRequest:
         read_title_intro=getattr(thread, "read_title_intro", False),
         read_closing_outro=getattr(thread, "read_closing_outro", True),
         auto_prefix_chapter_titles=getattr(thread, "auto_prefix_chapter_titles", True),
-        normalize_chapter_opening_caps=getattr(thread, "normalize_chapter_opening_caps", False),
+        normalize_chapter_opening_caps=thread.normalize_chapter_opening_caps,
         # Metadata
         metadata_tags=getattr(thread, "metadata_tags", {}) or {},
         # Artifacts

abogen/webui/conversion_runner.py

@@ -474,7 +474,7 @@ def run_conversion_job(job: Job) -> None:
             heading_text = spoken_title or raw_title
             chapter_display_title = heading_text or f"Chapter {idx}"
             job.add_log(f"Processing chapter {idx}/{total_chapters}: {chapter_display_title}")
-            normalize_opening_caps = bool(getattr(job, "normalize_chapter_opening_caps", True))
+            normalize_opening_caps = bool(job.normalize_chapter_opening_caps)
 
             chapter_start_time = current_time
             chapter_override = (