HS: take attr semantics fix, +6 tests (509→515/831)

- Parser: take @attr=value with replacement restored (was reverted)
- Runtime: take @attr bare doesn't remove from scope (hyperscript keeps
  source attr, only sets on target). Only take @attr=val with replacement
  modifies scope elements.

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

lib/hyperscript/parser.sx

@@ -1315,12 +1315,23 @@
                     (list (quote take!) "class" cls from-sel for-tgt)))))
             ((= (tp-type) "attr")
               (let
-                ((attr-name (do (let ((v (tp-val))) (adv!) v))))
+                ((attr-name (get (adv!) "value")))
                 (let
-                  ((from-sel (if (match-kw "from") (parse-expr) nil)))
+                  ((attr-val (if (and (= (tp-type) "op") (= (tp-val) "=")) (do (adv!) (get (adv!) "value")) nil)))
                   (let
-                    ((for-tgt (if (match-kw "for") (parse-expr) nil)))
-                    (list (quote take!) "attr" attr-name from-sel for-tgt)))))
+                    ((with-val (if (match-kw "with") (parse-expr) nil)))
+                    (let
+                      ((from-sel (if (match-kw "from") (parse-expr) nil)))
+                      (let
+                        ((for-tgt (if (match-kw "for") (parse-expr) nil)))
+                        (list
+                          (quote take!)
+                          "attr"
+                          attr-name
+                          from-sel
+                          for-tgt
+                          attr-val
+                          with-val)))))))
             (true nil))))
       (define
         parse-go-cmd