Update reference SX spec to match sx.js macros branch (CSSX, dict literals, new primitives)

- eval.sx: Add defstyle, defkeyframes, defhandler special forms; add ho-for-each
- parser.sx: Add dict {...} literal parsing and quasiquote/unquote sugar
- primitives.sx: Add parse-datetime, split-ids, css, merge-styles primitives
- render.sx: Add StyleValue handling, SVG filter elements, definition forms in render, fix render-to-html to handle HTML tags directly
- bootstrap_js.py: Add StyleValue type, buildKeyframes, isEvery platform helper, new primitives (format-date, parse-datetime, split-ids, css, merge-styles), dict/quasiquote parser, expose render functions as primitives
- sx-ref.js: Regenerated — 132/132 tests passing

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

shared/sx/ref/primitives.sx

@@ -426,3 +426,34 @@
   :params (s)
   :returns "string"
   :doc "Remove HTML tags from string.")
+
+
+;; --------------------------------------------------------------------------
+;; Date & parsing helpers
+;; --------------------------------------------------------------------------
+
+(define-primitive "parse-datetime"
+  :params (s)
+  :returns "string"
+  :doc "Parse datetime string — identity passthrough (returns string or nil).")
+
+(define-primitive "split-ids"
+  :params (s)
+  :returns "list"
+  :doc "Split comma-separated ID string into list of trimmed non-empty strings.")
+
+
+;; --------------------------------------------------------------------------
+;; CSSX — style system primitives
+;; --------------------------------------------------------------------------
+
+(define-primitive "css"
+  :params (&rest atoms)
+  :returns "style-value"
+  :doc "Resolve style atoms to a StyleValue with className and CSS declarations.
+        Atoms are keywords or strings: (css :flex :gap-4 :hover:bg-sky-200).")
+
+(define-primitive "merge-styles"
+  :params (&rest styles)
+  :returns "style-value"
+  :doc "Merge multiple StyleValues into one combined StyleValue.")