Fix compiler: handle clause-syntax cond — (cond (test body) ...)

compile-cond expected flat syntax (cond test body test body ...) but
hs-parse uses clause syntax (cond (test body) (test body) ...). The
compiler treated the whole clause as the test expression, compiling
((and ...) (do ...)) as a function call — which tried to call the
and-result as a function, producing "not callable: false" JIT errors.

Now detects clause syntax (first arg is a list whose first element is
also a list) and flattens to the expected format before compilation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/compiler.sx

@@ -724,38 +724,41 @@
       compile-cond
       (fn
         (em args scope tail?)
-        "Compile (cond test1 body1 test2 body2 ... :else fallback)."
-        (if
-          (< (len args) 2)
-          (emit-op em 2)
-          (let
-            ((test (first args))
-              (body (nth args 1))
-              (rest-clauses (if (> (len args) 2) (slice args 2) (list))))
-            (if
-              (or
-                (and
-                  (= (type-of test) "keyword")
-                  (= (keyword-name test) "else"))
-                (= test true))
-              (compile-expr em body scope tail?)
-              (do
-                (compile-expr em test scope false)
-                (emit-op em 33)
-                (let
-                  ((skip (current-offset em)))
-                  (emit-i16 em 0)
-                  (compile-expr em body scope tail?)
-                  (emit-op em 32)
+        "Compile (cond test1 body1 test2 body2 ... :else fallback).\n     Also handles clause syntax: (cond (test1 body1) (test2 body2) ...)."
+        (let
+          ((flat-args (if (and (not (empty? args)) (list? (first args)) (> (len (first args)) 1) (list? (first (first args)))) (reduce (fn (acc clause) (if (list? clause) (append acc clause) (append acc (list clause)))) (list) args) args)))
+          (if
+            (< (len flat-args) 2)
+            (emit-op em 2)
+            (let
+              ((test (nth flat-args 0))
+                (body (nth flat-args 1))
+                (rest-clauses
+                  (if (> (len flat-args) 2) (slice flat-args 2) (list))))
+              (if
+                (or
+                  (and
+                    (= (type-of test) "keyword")
+                    (= (keyword-name test) "else"))
+                  (= test true))
+                (compile-expr em body scope tail?)
+                (do
+                  (compile-expr em test scope false)
+                  (emit-op em 33)
                   (let
-                    ((end-jump (current-offset em)))
+                    ((skip (current-offset em)))
                     (emit-i16 em 0)
-                    (patch-i16 em skip (- (current-offset em) (+ skip 2)))
-                    (compile-cond em rest-clauses scope tail?)
-                    (patch-i16
-                      em
-                      end-jump
-                      (- (current-offset em) (+ end-jump 2)))))))))))
+                    (compile-expr em body scope tail?)
+                    (emit-op em 32)
+                    (let
+                      ((end-jump (current-offset em)))
+                      (emit-i16 em 0)
+                      (patch-i16 em skip (- (current-offset em) (+ skip 2)))
+                      (compile-cond em rest-clauses scope tail?)
+                      (patch-i16
+                        em
+                        end-jump
+                        (- (current-offset em) (+ end-jump 2))))))))))))
     (define
       compile-case
       (fn