fix(entity-io): reject unsafe entity type values before joining paths

Validate entity_type against a safe pattern to prevent path traversal
(e.g. ../outside or /tmp/escape) when constructing the subdirectory.

Addresses CodeRabbit review finding: Reject unsafe type values before joining paths

Author: vinodmut

plugins/kaizen/lib/entity_io.py

@@ -252,6 +252,8 @@ def write_entity_file(directory, entity):
         Path to the written file.
     """
     entity_type = entity.get("type", "general")
+    if not re.fullmatch(r"[a-z0-9][a-z0-9_-]*", entity_type):
+        entity_type = "general"
     type_dir = Path(directory) / entity_type
     type_dir.mkdir(parents=True, exist_ok=True)