core: Stage 2 Task 2 tier 5a — compile defmulti + defmethod

defmulti/defmethod become macros (30-macros) over ctx-capturing
clojure.core fns (defmulti-setup/defmethod-setup, interned by
install-stateful-fns!):
- defmulti: (defmulti name dispatch & opts) -> (defmulti-setup 'name
  dispatch ~@opts). name quoted; dispatch + opts (:default/:hierarchy)
  evaluated. defmulti-setup builds the dispatch closure over the method
  table and interns the var (same hierarchy/default/cache behavior).
- defmethod: (defmethod mm dval & fn-tail) -> (defmethod-setup 'mm dval
  (fn ~@fn-tail)). The method impl is now a COMPILED (fn …) (was an
  interpreted fn* eval). Auto-creates the multimethod if missing.
- removed their special-symbol? entries + eval-list arms, and dropped them
  from host_iface special-names + loader stateful-head?.

Both compile + interpret as plain invokes; dispatch incl. :default and
derive/hierarchy works in both modes.

Tests: evaluator-test (defmulti case) + namespace-test now use init (these
forms are overlay macros now, so a bare make-ctx lacks them).

Gate green: conformance 269x3, fallback-zero 38/4, bootstrap-fixpoint
stage1==2==3, self-host, staged-bootstrap, sci-bootstrap, clojure-test-suite
>=4034/67, features 78/78, all unit + spec (multimethods 16/16).

jolt-core/clojure/core/30-macros.clj

@@ -12,6 +12,16 @@
 
 (defmacro comment [& body] nil)
 
+;; defmulti/defmethod are sugar over defmulti-setup/defmethod-setup (ctx-capturing
+;; clojure.core fns) so they compile as plain invokes. name/mm are passed quoted;
+;; the dispatch fn, options, and dispatch value evaluate normally, and the method
+;; body becomes a compiled (fn …).
+(defmacro defmulti [name dispatch & opts]
+  `(defmulti-setup (quote ~name) ~dispatch ~@opts))
+
+(defmacro defmethod [mm dispatch-val & fn-tail]
+  `(defmethod-setup (quote ~mm) ~dispatch-val (fn ~@fn-tail)))
+
 ;; Single arglist (Jolt defmacro is single-arity); the optional else defaults nil
 ;; via rest-destructuring.
 (defmacro if-not [test then & [else]]