[Bug]: KeyError when using multiple PersistentClient instances with different paths in the same process (Python 3.13)

### What happened?

``import chromadb``
``client1 = chromadb.PersistentClient(path="./db1")``
``client2 = chromadb.PersistentClient(path="./db2") # raises KeyError``

When multiple PersistentClient instances are created with different paths in the same process, the identifier generated from persist_directory is not normalised, making ``_identifier_to_system`` cache lookup fail with a ``KeyError``.

### Versions

Python 3.13
Chroma latest version
Windows OS

### Relevant log output

```shell
File "chromadb/api/shared_system_client.py", line 49, in _create_system_if_not_exists
return cls._identifier_to_system[identifier]
KeyError: ''
```