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/writer.py

@@ -168,8 +168,19 @@ def write_chapter(chap, bp, folder, prev_sum, tracking=None, prev_content=None,
 
     pov_char = chap.get('pov_character', '')
 
-    # Use pre-loaded persona if provided (avoids re-reading sample files every chapter)
-    if prebuilt_persona is not None:
+    # Check for character-specific voice profile (Step 2: Character Voice Profiles)
+    character_voice = None
+    if pov_char:
+        for char in bp.get('characters', []):
+            if char.get('name') == pov_char and char.get('voice_profile'):
+                vp = char['voice_profile']
+                character_voice = f"Style/Bio: {vp.get('bio', '')}\nKeywords: {', '.join(vp.get('keywords', []))}"
+                utils.log("WRITER", f"  -> Using voice profile for POV character: {pov_char}")
+                break
+
+    if character_voice:
+        persona_info = character_voice
+    elif prebuilt_persona is not None:
         persona_info = prebuilt_persona
     else:
         persona_info = build_persona_info(bp) or "Standard, balanced writing style."