Hierarchy fns follow the reference contracts; deftype classes join the class graph

derive/underive/ancestors/descendants/parents/isa? re-ported from
clojure.core with the argument assertions and throw contracts intact:
derive asserts tag/parent shapes (AssertionError) and throws on redundant
or cyclic derivation; underive/derive on a non-hierarchy value throw at the
parents lookup (the map is called as a function, like the reference);
(descendants h SomeClass) throws UnsupportedOperationException. isa? gains
the reference's supers arm (a relationship derived on a class's super
applies to the class).

The class arms now answer fully through the one class graph: parents of a
class are its direct supers (bases), ancestors are the transitive set
rooted at java.lang.Object for concrete classes (interfaces are marked and
don't root at Object, matching getSuperclass semantics). deftype/defrecord
classes register into the graph at definition — protocol interfaces they
implement appear as supers (JVM-munged ns spelling), records carry the
record interfaces (IRecord/IPersistentMap/... whose closure supplies
Associative/Seqable), bare deftypes carry IType. The type NAME var still
holds the ctor (a jolt-ism); class-key maps it back to the class so
(ancestors TypeName)/(isa? x TypeName) work. canonical-host-tag learned to
NOT canonicalize deftype names through the graph arm (extend-type on a
deftype was registering under the bare segment its values never report).

Five old corpus rows used non-namespaced derive tags that throw on the JVM
too; now namespaced. 8 new JVM-certified corpus rows; spec entries for the
hierarchy family; cts baseline 5730 -> 5781 pass (ancestors/derive/
descendants/parents/underive namespaces fully clean), 74 baselined
namespaces.

docs/spec/09-core-library.md

@@ -232,6 +232,56 @@ clojure-test-suite `core_test/special_symbol_qmark.cljc` and every
 
 ---
 
+### make-hierarchy, derive, underive, isa?, parents, ancestors, descendants — since 1.0
+
+```
+(make-hierarchy)
+(derive tag parent)            (derive h tag parent)
+(underive tag parent)          (underive h tag parent)
+(isa? child parent)            (isa? h child parent)
+(parents tag)  (ancestors tag)  (descendants tag)   ; + (f h tag) forms
+```
+
+**Semantics**
+
+- S1. A hierarchy is a pure value `{:parents {tag #{...}} :ancestors {...}
+  :descendants {...}}`; the 3-arity forms are pure, the shorter arities read and
+  mutate the global hierarchy.
+- S2. `isa?` is true when `(= child parent)`, when the host type system says
+  parent is assignable from child (both classes), when the relationship was
+  `derive`d — including a relationship derived on one of a class child's
+  supers — or component-wise for equal-length vectors.
+- S3. Class tags answer through the host type hierarchy: `(parents c)` includes
+  the class's direct supers (`bases` — a concrete class's chain roots at
+  `java.lang.Object`, an interface's does not); `(ancestors c)` is the
+  transitive set plus anything `derive`d on the class or its supers. A
+  deftype/defrecord class's ancestry includes its implemented protocol
+  interfaces and, for records, the record interfaces
+  (`clojure.lang.IRecord`/`IPersistentMap`/`Associative`/…; `clojure.lang.IType`
+  for a bare deftype).
+- S4. `derive` returns the updated hierarchy (3-arity) or nil (2-arity);
+  deriving a relationship that already holds transitively, or one that would
+  create a cycle, throws.
+
+**Errors**
+
+- X1. `derive` asserts its argument shapes: parent must be a namespaced Named
+  value; tag must be a class or a Named value (namespaced in the 2-arity
+  global form); `(derive h tag tag)` fails the `not=` assert. AssertionError.
+- X2. `underive`/`derive` with a non-hierarchy `h` throw at the parents
+  lookup (the map is called as a function, like the reference).
+- X3. `(descendants h SomeClass)` throws UnsupportedOperationException
+  ("Can't get descendants of classes") — Java type inheritance is not
+  enumerable downward.
+
+**Conformance**
+
+S1–S4, X1–X3 → corpus `hierarchy / *` rows; clojure-test-suite
+`core_test/{derive,underive,isa_…,parents,ancestors,descendants}.cljc`
+(all fully passing).
+
+---
+
 ## Authoring notes
 
 - Source examples from the ClojureDocs export (`clojuredocs-export.edn`,