core: fn*/let*/loop* are plain-symbol primitives, matching Clojure (jolt-f79)

jolt-f79 asked to compile destructuring in fn* rest params. Checking
against Clojure inverts the premise: Clojure's fn* REJECTS destructuring
at compile time ('fn params must be Symbols'; let*/loop* 'Bad binding
form, expected symbol'). So the self-hosted analyzer was already correct
— fn*/let*/loop* are plain-symbol primitives; the fn/let/loop/defn
MACROS desugar destructuring. The real defect was the interpreter
leniently destructuring raw fn*, and defn emitting raw fn* to rely on it.

Changes:
- evaluator: fn*/let*/loop* now reject non-symbol binding forms with
  Clojure's exact messages (require-symbol-params/plain-sym?), so the
  interpreter agrees with the analyzer + Clojure.
- 00-syntax: defn emits the fn MACRO (not raw fn*) so destructuring
  params desugar; unnamed, so self-recursion still resolves via the var.
- 00-syntax: completing that exposed a real gap — the overlay destructure
  fn didn't handle kwargs (a map pattern bound against a fn's sequential
  rest); it had only worked via the interpreter's destructure-bind. Added
  the seq->map coercion to the map? branch (sequential: 1 map elt => that
  map, else apply hash-map), matching destructure-bind so interpret ==
  compile.

Net: fn*/let*/loop* are plain-symbol primitives across interpreter,
analyzer, and Clojure; all real destructuring (fn/defn/let/loop/macro
params, incl kwargs & {:keys}) compiles through the macros with no
interpreter fallback. Regression spec added.

Gate green: conformance 267x3, fallback-zero 31/5, bootstrap-fixpoint
stage1==2==3, self-host, staged-bootstrap, lazy-infinite 44/44,
clojure-test-suite >=4034/67, sci-bootstrap, features 78/78, all
unit+spec (destructuring 50/50).

jolt-core/clojure/core/00-syntax.clj

@@ -102,11 +102,24 @@
                    (vloop 0 0 (conj (conj acc g) init)))
                (map? pat)
                  (let* [g (symbol (str (gensym)))
+                        gm (symbol (str (gensym)))
+                        ;; kwargs: a map pattern may bind against the sequential rest
+                        ;; of a fn — (& {:keys [...]}) — which is a seq of alternating
+                        ;; k/v args, or a single trailing map. Coerce like Clojure (and
+                        ;; like the interpreter's destructure-bind, so interpret/compile
+                        ;; agree): a sequential value with one map element is that map,
+                        ;; otherwise (apply hash-map). A real map value is used as-is, so
+                        ;; ordinary map destructuring is unaffected. g holds init once;
+                        ;; gm is the coerced map every lookup (and :as) reads from.
+                        coerce `(if (sequential? ~g)
+                                  (if (and (= 1 (count ~g)) (map? (first ~g)))
+                                    (first ~g)
+                                    (apply hash-map ~g))
+                                  ~g)
                         or-map (get pat :or)
                         as-sym (get pat :as)
-                        base (if as-sym
-                               (conj (conj (conj (conj acc g) init) as-sym) g)
-                               (conj (conj acc g) init))
+                        bound (conj (conj (conj (conj acc g) init) gm) coerce)
+                        base (if as-sym (conj (conj bound as-sym) gm) bound)
                         group
                           (fn* [a kw kind]
                             (let* [names (get pat kw)]
@@ -125,8 +138,8 @@
                                            fo (find-or or-map local)]
                                       (conj (conj aa (symbol local))
                                             (if (nth fo 0)
-                                              `(get ~g ~keyform ~(nth fo 1))
-                                              `(get ~g ~keyform)))))
+                                              `(get ~gm ~keyform ~(nth fo 1))
+                                              `(get ~gm ~keyform)))))
                                   a names)
                                 a)))
                         g1 (group base :keys :kw)
@@ -135,7 +148,7 @@
                    (reduce (fn* [a k]
                              (if (keyword? k)
                                a
-                               (proc k `(get ~g ~(get pat k)) a)))
+                               (proc k `(get ~gm ~(get pat k)) a)))
                            g3 (keys pat)))
                :else (throw (str "unsupported destructuring pattern"))))
          ploop
@@ -212,8 +225,11 @@
       (let [as (vec (map mk aftn))]
         (if nm `(fn* ~nm ~@as) `(fn* ~@as))))))
 
-;; defn: drop an optional leading docstring and attr-map, then (def name (fn* ...)).
-;; Both single- and multi-arity reduce to (fn* ~@body) — fn* takes either a params
+;; defn: drop an optional leading docstring and attr-map, then (def name (fn ...)).
+;; Emits the fn MACRO (not the fn* primitive) so destructuring params desugar — fn*
+;; requires plain symbols (like Clojure). Unnamed (as before): self-recursion
+;; resolves through the def'd var, so this only adds the desugaring step.
+;; Both single- and multi-arity reduce to (fn ~@body) — fn takes either a params
 ;; vector + body or a sequence of ([params] body) clauses, so no arity branching is
 ;; needed. (map? is true for symbol forms too, so guard the attr-map with symbol?.)
 ;; Defined before fresh-sym below, which is a defn-.
@@ -221,7 +237,7 @@
   (let [body (if (and (seq body) (string? (first body))) (rest body) body)
         body (if (and (seq body) (map? (first body)) (not (symbol? (first body))))
                (rest body) body)]
-    `(def ~fn-name (fn* ~@body))))
+    `(def ~fn-name (fn ~@body))))
 
 ;; Jolt doesn't enforce privacy, so defn- is just defn (matching how Clojure's own
 ;; defn- delegates to defn with :private metadata).