♻️ refactor(obikpartitionner): replace low-level I/O with obiskio::SKFileWriter

- Replace `limits` module and raw binary I/O with a new high-level abstraction using obiskio::SKFileWriter
- Remove `niffler` dependency and compression logic (Gzip/Zstd/Lz4/Bgzf)
- Simplify PartitionManager to manage partitioned file writers based on kmer hashing
  * Uses `n_partition_bits` for bitmask-based partition selection (2^n partitions)
- Add obiskio as a local dependency
Note: This is likely part of aligning with unified I/O primitives in the obiskio crate.

src/obikseq/Cargo.toml

@@ -5,6 +5,7 @@ edition = "2024"
 
 [dependencies]
 bitvec = "1"
+xxhash-rust = { version = "0.8.15", features = ["xxh3", "const_xxh3"] }
 
 [dev-dependencies]
 criterion2 = { version = "3", features = ["cargo_bench_support"] }