HS: add {prop: value; ...} CSS block syntax in add command

Parser:
- Handle brace-open token in parse-add-cmd
- Parse colon-separated property:value pairs until brace-close
- Produces (set-styles ((prop val) ...) target)

Compiler:
- set-styles → (do (dom-set-style target prop1 val1) ...)

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

lib/hyperscript/parser.sx

@@ -822,6 +822,32 @@
                 (let
                   ((tgt (if (match-kw "to") (parse-expr) (list (quote me)))))
                   (list (quote set-style) prop value tgt))))
+            ((= (tp-type) "brace-open")
+              (do
+                (adv!)
+                (let
+                  ((pairs (list)))
+                  (define
+                    collect-pairs!
+                    (fn
+                      ()
+                      (when
+                        (and
+                          (not (= (tp-type) "brace-close"))
+                          (not (at-end?)))
+                        (let
+                          ((prop (get (adv!) "value")))
+                          (when (= (tp-type) "colon") (adv!))
+                          (let
+                            ((val (tp-val)))
+                            (adv!)
+                            (set! pairs (cons (list prop val) pairs))
+                            (collect-pairs!))))))
+                  (collect-pairs!)
+                  (when (= (tp-type) "brace-close") (adv!))
+                  (let
+                    ((tgt (if (match-kw "to") (parse-expr) (list (quote me)))))
+                    (list (quote set-styles) (reverse pairs) tgt)))))
             (true
               (let
                 ((value (parse-expr)))