fix: validate packed matrix columns before repacking

Add header parsing helpers to extract column counts without memory mapping. Update packing functions to verify existing files match current metadata, preventing stale or widened-column artifacts. Extract inline tests in obilayeredmap to an external module and add comprehensive aggregation tests. Bump obikmer to 1.1.35 and clean up repository configuration.

.gitignore

@@ -15,6 +15,7 @@ benchmark/simulated_data
 benchmark/specimen_index_presence
 benchmark/specimen_index_count
 benchmark/global_index_presence
+benchmark/all_specific
 benchmark/global_index_count
 benchmark/stats
 benchmark/reference_index