fix: remove redundant isinstance check in blackboard.py

Author: jovanSAPFIONEER

scripts/blackboard.py

@@ -315,7 +315,7 @@ def _sanitize_change_id(change_id: str) -> str:
         Only allows alphanumeric characters, hyphens, underscores, and dots.
         Rejects any path separators or parent directory references.
         """
-        if not change_id or not isinstance(change_id, str):
+        if not change_id:
             raise ValueError("change_id must be a non-empty string")
         # Strip whitespace
         sanitized = change_id.strip()