HS: parse-feat keyword-first guard — fix assert-throws for command-like scripts (+2 tests)

parse-feat true fallback now routes directly to parse-cmd-list when the first
token is a keyword (e.g. "add - to"), so command-keyword scripts always produce
parse errors rather than being treated as subtraction expressions. Non-keyword
tokens (numbers, identifiers, paren-open) still try expression-first.

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

lib/hyperscript/parser.sx

@@ -3219,14 +3219,17 @@
                   "worker plugin is not installed — see https://hyperscript.org/features/worker"))
               ((= val "bind") (do (adv!) (parse-bind-feat)))
               (true
-                (let
-                  ((saved-p p))
+                (if
+                  (= (tp-type) "keyword")
+                  (parse-cmd-list)
                   (let
-                    ((expr (guard (_e (true nil)) (parse-expr))))
-                    (if
-                      (and expr (at-end?))
-                      expr
-                      (do (set! p saved-p) (parse-cmd-list))))))))))
+                    ((saved-p p))
+                    (let
+                      ((expr (guard (_e (true nil)) (parse-expr))))
+                      (if
+                        (and expr (at-end?))
+                        expr
+                        (do (set! p saved-p) (parse-cmd-list)))))))))))
       (define
         coll-feats
         (fn