Hyperscript: focus command, diagnostic test output, blur keyword

Parser/compiler/runtime for focus command. Tokenizer: focus, blur,
precedes, follows, ignoring, case keywords. Test spec: per-test
failure output for diagnosis.

374/831 (45%)

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

lib/hyperscript/parser.sx

@@ -1266,6 +1266,13 @@
       (define
         parse-param-list
         (fn () (if (= (tp-type) "paren-open") (parse-call-args) (list))))
+      (define
+        parse-focus-cmd
+        (fn
+          ()
+          (let
+            ((tgt (cond ((at-end?) (list (quote me))) ((and (= (tp-type) "keyword") (or (= (tp-val) "then") (= (tp-val) "end"))) (list (quote me))) (true (parse-expr)))))
+            (list (quote focus!) tgt))))
       (define
         parse-feat-body
         (fn
@@ -1452,6 +1459,8 @@
                 (do (adv!) (parse-default-cmd)))
               ((and (= typ "keyword") (= val "halt"))
                 (do (adv!) (parse-halt-cmd)))
+              ((and (= typ "keyword") (= val "focus"))
+                (do (adv!) (parse-focus-cmd)))
               (true (parse-expr))))))
       (define
         parse-cmd-list
@@ -1496,7 +1505,8 @@
                 (= v "default")
                 (= v "scroll")
                 (= v "select")
-                (= v "reset"))))
+                (= v "reset")
+                (= v "focus"))))
           (define
             cl-collect
             (fn