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/compiler.sx

@@ -856,6 +856,16 @@
                   (hs-to-sx (nth ast 3))
                   (nth ast 1)
                   (nth ast 2)))
+              ((= head (quote set-styles))
+                (let
+                  ((pairs (nth ast 1)) (tgt (hs-to-sx (nth ast 2))))
+                  (cons
+                    (quote do)
+                    (map
+                      (fn
+                        (p)
+                        (list (quote dom-set-style) tgt (first p) (nth p 1)))
+                      pairs))))
               ((= head (quote multi-add-class))
                 (let
                   ((target (hs-to-sx (nth ast 1)))