refactor: restructure k-mer partitioning pipeline for memory efficiency

Replace in-memory hashing with a disk-backed external merge sort and `PersistentCompactIntVec` to drastically reduce peak RAM. Unify both phases using a custom `PtrHash` MPHF, eliminating `GOFunction` and `boomphf`. Introduce a concrete three-step `count_partition()` pipeline with adaptive chunk sizing based on available system memory. Update dependencies to `memmap2`, `ptr_hash`, and `obicompactvec`. Additionally, document strict genomics-only memory constraints and enforce an architectural feedback workflow requiring explicit user authorization before structural changes.

src/Cargo.lock

@@ -1745,14 +1745,17 @@ dependencies = [
 name = "obikpartitionner"
 version = "0.1.0"
 dependencies = [
+ "cacheline-ef",
+ "epserde 0.8.0",
  "memmap2",
  "niffler 3.0.0",
+ "obicompactvec",
  "obikrope",
  "obikseq",
  "obiread",
  "obiskbuilder",
  "obiskio",
- "ph",
+ "ptr_hash",
  "rayon",
  "remove_dir_all",
  "serde",
@@ -1842,6 +1845,13 @@ dependencies = [
  "tempfile",
 ]
 
+[[package]]
+name = "obisys"
+version = "0.1.0"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "objc2-core-foundation"
 version = "0.3.2"