fix(ontology): rename backtracking_string_partition to backtracking_string_segmentation

The pattern name in patterns.toml was inconsistent with problem metadata
files (0093, 0131), causing these problems to not appear in generated
pattern_hierarchy.md mindmap.

Author: lufftw

ontology/patterns.toml

@@ -143,7 +143,7 @@ api_kernel = "BacktrackingExploration"
 summary = "Unique subsets with sorting and same-level deduplication."
 
 [[patterns]]
-id = "backtracking_string_partition"
+id = "backtracking_string_segmentation"
 api_kernel = "BacktrackingExploration"
 summary = "Partition string into valid segments (IP, palindromes)."