Fix reply-context speaker confusion with structured metadata pipeline

Previously, when a user replied to Miku's message via Discord's reply
feature, Miku's quoted words were embedded directly into the user's
message text using the format:
  [Replying to your message: "Miku's words"] User's response

This caused two problems:
1. The LLM had to parse "your message" to determine the quoted text
   was MIKU's words — fragile and frequently misattributed
2. When stored in episodic memory as [User]: ..., Miku's quoted words
   were permanently mislabeled under the user's speaker prefix

Now reply context flows through as structured metadata:
- bot/bot.py captures the replied-to text WITHOUT embedding it in prompt
- cat_client.py passes it as discord_reply_context in the WebSocket payload
- discord_bridge.py injects it as agent_input['reply_context'] — a
  CLEARLY LABELED note: [The user is replying to what you (Miku) said — ...]
- miku_personality.py + evil_miku_personality.py render it via
  {reply_context} placeholder in the prompt suffix, between memory
  context and conversation history

This keeps Miku's words as a separate context note, never mixed into
the user's HumanMessage. Episodic memory only stores the user's actual
words. The fallback path (when Cat is unavailable) also uses a cleaner
format with explicit speaker labels.

bot/utils/cat_client.py

@@ -109,6 +109,7 @@ class CatAdapter:
         mood: Optional[str] = None,
         response_type: str = "dm_response",
         media_type: Optional[str] = None,
+        reply_context: Optional[str] = None,
     ) -> Optional[tuple]:
         """
         Send a message through the Cat pipeline via WebSocket and get a response.
@@ -162,6 +163,12 @@ class CatAdapter:
         # Pass media type so discord_bridge can add MEDIA NOTE to the prompt
         if media_type:
             payload["discord_media_type"] = media_type
+        # Pass the message the user is replying to (if any) as structured metadata.
+        # The discord_bridge plugin injects this into the prompt as a clearly-labeled
+        # context note — keeping Miku's words separate from the user's message text
+        # and preventing the speaker confusion that the old embed-in-prompt format caused.
+        if reply_context:
+            payload["discord_reply_context"] = reply_context
         # Pass current Discord activity if it changed recently (30-min decay window)
         activity_label = get_current_activity_fresh()
         if activity_label: