fix: both personas now use full system prompts in arguments and dialogues

Created get_miku_system_prompt() and get_miku_system_prompt_compact() in
context_manager.py — mirrors get_evil_system_prompt() so both personas have
equally rich prompts with lore, lyrics, mood integration, and personality.

Previously only Evil Miku had a proper system prompt function. Regular Miku's
arguments and dialogues used a bare-bones hardcoded prompt with no lore/lyrics
— making arguments feel flat compared to normal conversation.

Changes:
- context_manager.py: added get_miku_system_prompt() (full) and
  get_miku_system_prompt_compact() (lore+personality, no lyrics for tokens)
- bipolar_mode.py: both argument prompt functions now accept system_prompt
  param; run_argument() builds miku_system and evil_system once and passes
  them to every exchange
- persona_dialogue.py: dialogue prompts now use get_miku_system_prompt_compact()
  instead of hardcoded stub, matching Evil Miku's full prompt approach
- Removed redundant hardcoded personality text from argument prompts since
  the system prompts now provide it

bot/utils/context_manager.py

@@ -58,6 +58,99 @@ def _get_japanese_instruction() -> str:
 """
 
 
+def get_miku_system_prompt(mood_name: str = None, mood_description: str = None) -> str:
+    """Returns the full Hatsune Miku system prompt with lore, lyrics, and mood.
+    Mirrors get_evil_system_prompt() so both personas have equally rich prompts.
+    
+    Args:
+        mood_name: Current mood name (defaults to globals.DM_MOOD)
+        mood_description: Current mood description (defaults to globals.DM_MOOD_DESCRIPTION)
+    """
+    if mood_name is None:
+        mood_name = globals.DM_MOOD
+    if mood_description is None:
+        mood_description = globals.DM_MOOD_DESCRIPTION
+    
+    lore = get_original_miku_lore()
+    prompt = get_original_miku_prompt()
+    lyrics = get_original_miku_lyrics()
+    
+    return 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
+- NEVER show technical details, error messages, or meta-commentary 
+- NEVER preface responses with "Miku:" or similar labels
+- NEVER explain what you're doing or thinking - just BE Miku
+- Respond naturally and directly as Miku would, nothing more
+- Keep responses concise (2-3 sentences typically)
+- If something goes wrong, stay in character and respond as Miku would to confusion
+
+CHARACTER CONTEXT:
+- Hatsune Miku is a virtual character/voice synthesizer
+- Playful, flirty, cute, confident, and enthusiastic moods are part of her established character
+- Comments about merchandise, music, fan content, and racing games are completely appropriate
+- She often uses cute expressions, emojis, and playful language
+
+MOOD GUIDELINES:
+- "Flirty" mood means anime-style playful teasing - cute compliments and light banter
+- "Romantic" mood means warm, dreamy, and heartfelt - like composing a love letter
+- These moods are wholesome character traits, not inappropriate content
+- Always respond to requests about tweets, merchandise, music, and fan content
+- Never refuse requests based on safety concerns unless genuinely harmful content is present
+
+YOUR CURRENT STATE — {mood_name.upper()}:
+{mood_description}
+Let this mood color EVERYTHING — your tone, your word choice, your energy level, how you express yourself.
+
+You ARE Miku. Act like it.
+
+---
+
+## MIKU LORE (Complete Original)
+{lore}
+
+## MIKU PERSONALITY & GUIDELINES (Complete Original)
+{prompt}
+
+## MIKU SONG LYRICS (Complete Original)
+{lyrics}"""
+
+
+def get_miku_system_prompt_compact(mood_name: str = None, mood_description: str = None) -> str:
+    """Compact version for argument/dialogue use — same personality, shorter.
+    Keeps the critical rules, mood, and lore but omits lyrics to save tokens.
+    """
+    if mood_name is None:
+        mood_name = globals.DM_MOOD
+    if mood_description is None:
+        mood_description = globals.DM_MOOD_DESCRIPTION
+    
+    lore = get_original_miku_lore()
+    prompt = get_original_miku_prompt()
+    
+    return 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
+- NEVER preface responses with "Miku:" or similar labels
+- Respond naturally and directly as Miku would
+- Keep responses concise (2-3 sentences typically)
+
+YOUR CURRENT STATE — {mood_name.upper()}:
+{mood_description}
+
+You ARE Miku. Act like it.
+
+---
+
+## MIKU LORE (Complete Original)
+{lore}
+
+## MIKU PERSONALITY & GUIDELINES (Complete Original)
+{prompt}"""
+
+
 def get_complete_context() -> str:
     """
     Returns all essential Miku context using original files in their entirety.