refactor: rename obikpartitionner crate to obikpartition

Update Cargo manifests, dependency paths, and Rust imports across the workspace to reflect the `obikpartitionner` to `obikpartition` rename. Synchronize architecture and implementation documentation with the new module structure. Fix minor syntax issues in test assertions to ensure compilation compatibility. No behavioral or API changes are introduced.

DevDocMD/theory/evolutionary_distances.md

@@ -1489,7 +1489,7 @@ instead of a per-partition `partial_*`, run the sequential source sweep:
 
 ```text
 for p in 0..n_partitions:                       # OUTER — sequential
-    open source partition p's layers (QueryLayer-style, obikpartitionner)
+    open source partition p's layers (QueryLayer-style, obikpartition)
     enumerate distinct canonical k-mers of p (one per MPHF slot) with their
         presence/count vectors                   # column-major, as query stage 2
     par_iter over these source k-mers:           # INNER — rayon, thread-local tally
@@ -1513,7 +1513,7 @@ for p in 0..n_partitions:                       # OUTER — sequential
 ```
 
 The inner lookup is precisely `QueryLayer::find_slot` +
-`col_value(g, slot)` (`obikpartitionner/src/query_layer.rs`) — reuse or factor
+`col_value(g, slot)` (`obikpartition/src/query_layer.rs`) — reuse or factor
 out that path rather than reimplementing MPHF access. Enumerating "all distinct
 k-mers of a partition with their vectors" is the `dump`/`query` stage-2
 column-major scan already implemented in `dump_layer.rs` /