core: Stage 2 Task 2 tier 1 — compile syntax-quote + definterface/extend/proxy

First slice of moving stateful forms onto the compile path (jolt-eaa).
- loader stateful-head?: drop syntax-quote (the analyzer's `handled` set
  already compiles it; routing it to the interpreter was redundant).
- host_iface special-names: drop definterface/extend/proxy (stub macros
  expanding to def/nil — their expansions compile once unpunted).
- letfn stays interpreted: its let* expansion needs letrec semantics
  (mutual recursion between the fns), which sequential compiled let* lacks
  — a later tier.

Gate green: conformance 267x3, fallback-zero 31/5, bootstrap-fixpoint
stage1==2==3, self-host, staged-bootstrap, clojure-test-suite >=4034/67,
features 78/78, all unit + protocol/multimethod/macro specs.

src/jolt/host_iface.janet

@@ -81,8 +81,10 @@
              "create-ns" "remove-ns" "find-ns" "all-ns" "the-ns" "resolve"
              "ns-resolve" "ns-aliases" "ns-imports" "ns-interns"
              "read-string" "macroexpand-1" "defonce" "ns" "in-ns" "require"
-             "import" "use" "refer" "defrecord" "defprotocol" "definterface"
-             "reify" "proxy" "extend-type" "extend-protocol" "extend" "gen-class"
+             "import" "use" "refer" "defrecord" "defprotocol"
+             "reify" "extend-type" "extend-protocol" "gen-class"
+             # letfn stays: its let* expansion needs letrec semantics (mutual
+             # recursion between the fns), which compiled sequential let* lacks.
              "monitor-enter" "monitor-exit" "binding" "letfn"]
       (put t n true))
     t))

src/jolt/loader.janet

@@ -9,12 +9,14 @@
 # Stateful / context-modifying forms always interpret: they mutate the context
 # (namespaces, macros, types, multimethods, dynamic vars, …) in ways the compiler
 # doesn't model. Kept here so the compile/interpret routing lives in one place,
-# used by both load-ns and the public eval-one.
+# used by both load-ns and the public eval-one. Shrinking toward the frozen
+# host-coupled set (Stage 2 jolt-eaa): forms move off this list as they gain a
+# compile path; syntax-quote already compiles via the analyzer's `handled` set.
 (defn- stateful-head? [head-name]
   (or (= head-name "defmacro") (= head-name "ns")
       (= head-name "deftype") (= head-name "defmulti") (= head-name "defmethod")
       (= head-name "require") (= head-name "in-ns")
-      (= head-name "syntax-quote") (= head-name "set!")
+      (= head-name "set!")
       (= head-name "var") (= head-name ".") (= head-name "new")
       (= head-name "eval")))