docs: fix partition_pattern order preservation

The partition_pattern was not preserving the order of attributes specified
in the pattern because it was iterating over a set (unordered). This caused
paths like 'neuron_id=0/mouse_id=5/session_date=2017-01-05/...' instead of
the expected 'mouse_id=5/session_date=2017-01-05/neuron_id=0/...'.

Changes:
- Extract partition attributes as a list to preserve order
- Keep a set for efficient lookup when filtering remaining PK attributes
- Iterate over the ordered list when building partition path components

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

Author: dimitri-yatsenko

src/datajoint/storage.py

@@ -234,16 +234,19 @@ def build_object_path(
     # Build primary key path components
     pk_parts = []
     partition_attrs = set()
+    partition_attr_list = []
 
     # Extract partition attributes if pattern specified
     if partition_pattern:
         import re
 
-        partition_attrs = set(re.findall(r"\{(\w+)\}", partition_pattern))
+        # Preserve order from pattern
+        partition_attr_list = re.findall(r"\{(\w+)\}", partition_pattern)
+        partition_attrs = set(partition_attr_list)  # For fast lookup
 
-    # Build partition prefix (attributes specified in partition pattern)
+    # Build partition prefix (attributes in order from partition pattern)
     partition_parts = []
-    for attr in partition_attrs:
+    for attr in partition_attr_list:
         if attr in primary_key:
             partition_parts.append(f"{attr}={encode_pk_value(primary_key[attr])}")