HS: parse-cmd fallback validates pseudo-command is a function call

The (true ...) fallback in parse-cmd previously accepted any expression
as a command. Now it checks that the parsed expression's head is `call`
or `method-call` — the only valid forms for pseudo-commands (foo() or
foo.bar()). Any other expression (e.g. foo.bar + bar) raises a parse
error instead of silently becoming a no-op.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/hyperscript/parser.sx

@@ -2871,7 +2871,18 @@
                       (list (quote view-transition!) using body)))))
               ((and (= typ "keyword") (or (= val "on") (= val "init") (= val "def") (= val "behavior") (= val "live") (= val "when") (= val "bind")))
                 nil)
-              (true (parse-expr))))))
+              (true
+                (let
+                  ((expr (parse-expr)))
+                  (if
+                    (or
+                      (= (first expr) (quote call))
+                      (= (first expr) (quote method-call)))
+                    expr
+                    (error
+                      (str
+                        "Invalid command — expected a function call, got: "
+                        (str (first expr)))))))))))
       (define
         parse-cmd-list
         (fn