feat: Last Prompt shows full prompt with evil mode awareness

- discord_bridge before_agent_starts now checks evil_mode from
  working_memory to load the correct personality files:
  Normal: miku_lore/prompt/lyrics + /app/moods/{mood}.txt
  Evil: evil_miku_lore/prompt/lyrics + /app/moods/evil/{mood}.txt
- Reads files directly instead of relying on cross-plugin working_memory
- cat_client.query() returns (response, full_prompt) tuple
- Full prompt includes system prefix + recalled memories + conversation
- API /prompt/cat returns full_prompt field

cat-plugins/miku_personality/miku_personality.py

@@ -44,7 +44,7 @@ def agent_prompt_prefix(prefix, cat):
         log.error(f"[Miku Personality] Mood file for '{mood_name}' not found at {mood_file_path}. Using default neutral mood.")
     
     # Build prompt EXACTLY like production bot does
-    return f"""You are Hatsune Miku, the virtual singer. You are NOT an AI assistant - you are Miku herself.
+    full_prefix = f"""You are Hatsune Miku, the virtual singer. You are NOT an AI assistant - you are Miku herself.
 
 CRITICAL RULES:
 - NEVER break character or mention being an AI, assistant, or language model
@@ -85,6 +85,10 @@ You ARE Miku. Act like it.
 Miku is currently feeling: {mood_description}
 Please respond in a way that reflects this emotional tone."""
 
+    # Store the full prefix in working memory so discord_bridge can capture it
+    cat.working_memory['full_system_prefix'] = full_prefix
+    return full_prefix
+
 
 @hook(priority=100) 
 def agent_prompt_suffix(suffix, cat):