Extract phylogenetic sibling logic into new obikphylo crate

Relocate the `siblings` and `cardcomp` modules from `obikindex` to a dedicated `obikphylo` workspace member. Convert inherent methods on `KmerIndex` into extension traits, update import paths across `obikmer`, and add supporting accessor methods to `obikseq` and `obilayeredmap`. This restructuring reduces the public API surface of `obikindex` while organizing phylogenetic iteration, caching, and distance calculation logic under a dedicated crate.

src/obikphylo/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "obikphylo"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+obikindex        = { path = "../obikindex" }
+obikseq          = { path = "../obikseq" }
+obikpartitionner = { path = "../obikpartitionner" }
+obiskio          = { path = "../obiskio" }
+obisys           = { path = "../obisys" }
+obicompactvec    = { path = "../obicompactvec" }
+obilayeredmap    = { path = "../obilayeredmap" }
+obiskbuilder     = { path = "../obiskbuilder" }
+obipipeline      = { path = "../obipipeline" }
+ndarray          = "0.16"
+rayon            = "1"
+tracing          = "0.1.44"
+
+[dev-dependencies]
+obiread  = { path = "../obiread" }
+tempfile = "3"
+tracing-subscriber = { version = "0.3", features = ["fmt", "env-filter"] }