fix: switch to zephyr-7b-beta with chat_completion

pipeline/explainer.py

@@ -21,7 +21,7 @@ FALLACY_DEFINITIONS = {
     "intentional": "A deliberate and deceptive use of misleading reasoning"
 }
 
-DEFAULT_MODEL_ID = "mistralai/Mistral-7B-Instruct-v0.3"
+DEFAULT_MODEL_ID = "HuggingFaceH4/zephyr-7b-beta"
 
 
 class FallacyExplainer:
@@ -39,12 +39,12 @@ class FallacyExplainer:
         print(f"FallacyExplainer ready (model: {model_id})")
 
     def _generate_with_prompt(self, prompt_text, max_new_tokens=128):
-        return self._client.text_generation(
-            prompt_text,
-            max_new_tokens=max_new_tokens,
+        result = self._client.chat_completion(
+            messages=[{"role": "user", "content": prompt_text}],
+            max_tokens=max_new_tokens,
             temperature=0.1,
-            do_sample=True,
-        ).strip()
+        )
+        return result.choices[0].message.content.strip()
 
     def _load_prompt(self, path):
         with open(BASE_DIR / path, "r") as f: