Chain exceptions in _load_catalog_config for both catalog classes

Add 'from exc' to preserve root cause in tracebacks while keeping
clean user-facing messages.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: mnriem

src/specify_cli/workflows/catalog.py

@@ -182,7 +182,7 @@ def _load_catalog_config(
         except (yaml.YAMLError, OSError, UnicodeError) as exc:
             raise WorkflowValidationError(
                 f"Failed to read catalog config {config_path}: {exc}"
-            )
+            ) from exc
         if not isinstance(data, dict):
             raise WorkflowValidationError(
                 f"Invalid catalog config: expected a mapping, "
@@ -797,7 +797,7 @@ def _load_catalog_config(
         except (yaml.YAMLError, OSError, UnicodeError) as exc:
             raise StepValidationError(
                 f"Failed to read catalog config {config_path}: {exc}"
-            )
+            ) from exc
         if not isinstance(data, dict):
             raise StepValidationError(
                 f"Invalid catalog config: expected a mapping, "