log(llm_core): add warnings to silent except Exception blocks

- Malformed URL in _is_ollama_native_url now logs a warning so bad
  endpoint configs are traceable instead of silently returning False.
- Model list fetch failure now logs a warning with the endpoint URL so
  endpoints that silently vanish from the model picker are diagnosable.

src/llm_core.py

@@ -283,7 +283,8 @@ def _is_ollama_native_url(url: str) -> bool:
     """Return True for native Ollama API URLs, including Ollama Cloud."""
     try:
         parsed = urlparse(url or "")
-    except Exception:
+    except Exception as e:
+        logger.warning("Failed to parse URL for Ollama detection %r: %s", url, e)
         return False
     host = parsed.hostname or ""
     path = (parsed.path or "").rstrip("/")
@@ -1345,8 +1346,8 @@ def list_model_ids(
                 r = httpx.get(root + "/api/tags", timeout=timeout)
                 r.raise_for_status()
                 return [m.get("name") or m.get("model") for m in (r.json().get("models") or []) if m.get("name") or m.get("model")]
-        except Exception:
-            pass
+        except Exception as e:
+            logger.warning("Failed to fetch model list from endpoint %r: %s", base_chat_url, e)
         return []
 
 def normalize_model_id(