chore: improve log messages for vendor and model fallback

Author: ksylvan

src/fabric_mcp/core.py

@@ -372,15 +372,15 @@ def get_vendor_and_model(self, config: PatternExecutionConfig) -> tuple[str, str
         vendor_name = self._default_vendor
         if not vendor_name:
             self.logger.debug(
-                "Vendor name is None. Falling back to hardcoded default vendor: %s",
+                "Vendor name is None or empty. Set to hardcoded default vendor: %s",
                 DEFAULT_VENDOR,
             )
             vendor_name = DEFAULT_VENDOR
 
         model_name = config.model_name or self._default_model
         if not model_name:
             self.logger.debug(
-                "Model name is None. Falling back to hardcoded default model: %s",
+                "Model name is None or empty. Set to hardcoded default model: %s",
                 DEFAULT_MODEL,
             )
             model_name = DEFAULT_MODEL