fix: validate builtin arity before argument access

tests/38_builtin_arity.claro

@@ -0,0 +1,26 @@
+IMPORT "lib/math.claro" AS math
+IMPORT "lib/random.claro" AS random
+
+TRY
+    CALL math.abs
+CATCH
+ENDTRY
+SAY LASTERROR
+
+TRY
+    CALL math.clamp WITH 1, 0
+CATCH
+ENDTRY
+SAY LASTERROR
+
+TRY
+    CALL random.seed
+CATCH
+ENDTRY
+SAY LASTERROR
+
+TRY
+    CALL random.int WITH 1
+CATCH
+ENDTRY
+SAY LASTERROR

tests/38_builtin_arity.out

@@ -0,0 +1,4 @@
+math.abs needs 1 argument, but got 0. Try: CALL math.abs WITH value.
+math.clamp needs 3 arguments, but got 2. Try: CALL math.clamp WITH value, lower, upper.
+random.seed needs 1 argument, but got 0. Try: CALL random.seed WITH value.
+random.int needs 2 arguments, but got 1. Try: CALL random.int WITH lower, upper.