feat: Implement ai_blueprint.md Steps 1 & 2 — bible-tracking merge and character voice profiles

Step 1 (Bible-Tracking Merge):
- Added merge_tracking_to_bible() to story/bible_tracker.py — merges character
  tracking state and lore back into bible dict after each chapter, making
  blueprint_initial.json the single persistent source of truth.
- Integrated in cli/engine.py after each chapter's update_tracking + update_lore_index
  calls so the persisted bible is always up-to-date.

Step 2 (Character-Specific Voice Profiles):
- story/writer.py: write_chapter now checks bp['characters'] for a voice_profile on
  the POV character before falling back to the prebuilt_persona cache.
- story/style_persona.py: refine_persona() accepts pov_character=None; when a POV
  character with a voice_profile is supplied it refines that profile's bio instead of
  the global author_details bio.
- cli/engine.py: refine_persona call now passes ch.get('pov_character') so per-chapter
  persona refinement targets the correct voice.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

story/bible_tracker.py

@@ -141,6 +141,30 @@ def update_lore_index(folder, chapter_text, current_lore):
         return current_lore
 
 
+def merge_tracking_to_bible(bible, tracking):
+    """Merge dynamic tracking state back into the bible dict.
+
+    Makes bible.json the single persistent source of truth by updating
+    character data and lore from the in-memory tracking object.
+    Returns the modified bible dict.
+    """
+    for name, data in tracking.get('characters', {}).items():
+        matched = False
+        for char in bible.get('characters', []):
+            if char.get('name') == name:
+                char.update(data)
+                matched = True
+                break
+        if not matched:
+            utils.log("TRACKER", f"  -> Character '{name}' in tracking not found in bible. Skipping.")
+
+    if 'lore' not in bible:
+        bible['lore'] = {}
+    bible['lore'].update(tracking.get('lore', {}))
+
+    return bible
+
+
 def harvest_metadata(bp, folder, full_manuscript):
     utils.log("HARVESTER", "Scanning for new characters...")
     full_text = "\n".join([c.get('content', '') for c in full_manuscript])[:500000]