Enable thinking for chat, diversify roast styles

- Remove /no_think override from chat() so Qwen3 reasons before
  generating responses (fixes incoherent word-salad replies)
- Analysis and image calls keep /no_think for speed
- Add varied roast style guidance (deadpan, sarcastic, blunt, etc.)
- Explicitly ban metaphors/similes in roast prompt
- Replace metaphor examples with direct roast examples

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

utils/llm_client.py

@@ -306,10 +306,7 @@ class LLMClient:
         first content token arrives (useful for triggering the typing indicator
         only after the model starts generating).
         """
-        # Append /no_think to the last user message for local Qwen models
         patched = list(messages)
-        if self._no_think and patched and patched[-1].get("role") == "user":
-            patched[-1] = {**patched[-1], "content": self._append_no_think(patched[-1]["content"])}
 
         req_json = json.dumps([
             {"role": "system", "content": system_prompt[:500]},