feat(models): auto-mode intent remap + real coder models in preference

Settings "Auto model routing" picks which installed model fires for chat vs
coding intent when no model is pinned (auto_chat_model / auto_code_model).
_auto_select_model honors the remap; _MODEL_PREFERENCE["code"] prefers real
coder models first.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

synapse/main.py

@@ -104,6 +104,11 @@ async def _auto_select_model(message: str = "") -> str:
         if s.get("model"):
             return s["model"]
         intent = _detect_intent(message) if message else "chat"
+        # Auto-mode remap: a configured model for this intent fires first;
+        # otherwise fall back to the built-in preference list.
+        remap = s.get(f"auto_{intent}_model")
+        if remap:
+            return remap
         return await get_ollama_manager().select_best_model(intent)
     except Exception:
         return DEFAULT_CHAT_MODEL