Remove CSSX style dictionary infrastructure — styling is just components

The entire parallel CSS system (StyleValue type, style dictionary,
keyword atom resolver, content-addressed class generation, runtime
CSS injection, localStorage caching) was built but never adopted —
the codebase already uses :class strings with defcomp components
for all styling. Remove ~3,000 lines of unused infrastructure.

Deleted:
- cssx.sx spec module (317 lines)
- style_dict.py (782 lines) and style_resolver.py (254 lines)
- StyleValue type, defkeyframes special form, build-keyframes platform fn
- Style dict JSON delivery (<script type="text/sx-styles">), cookies, localStorage
- css/merge-styles primitives, inject-style-value, fnv1a-hash platform interface

Simplified:
- defstyle now binds any value (string, function) — no StyleValue type needed
- render-attrs no longer special-cases :style StyleValue → class conversion
- Boot sequence skips style dict init step

Preserved:
- tw.css parsing + CSS class delivery (SX-Css headers, <style id="sx-css">)
- All component infrastructure (defcomp, caching, bundling, deps)
- defstyle as a binding form for reusable class strings

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

shared/sx/ref/adapter-html.sx

@@ -41,7 +41,6 @@
       "boolean" (if val "true" "false")
       "list"    (render-list-to-html val env)
       "raw-html" (raw-html-content val)
-      "style-value" (style-value-class val)
       :else     (escape-html (str val)))))
 
 
@@ -51,7 +50,7 @@
 
 (define RENDER_HTML_FORMS
   (list "if" "when" "cond" "case" "let" "let*" "begin" "do"
-        "define" "defcomp" "defmacro" "defstyle" "defkeyframes" "defhandler"
+        "define" "defcomp" "defmacro" "defstyle" "defhandler"
         "map" "map-indexed" "filter" "for-each"))
 
 (define render-html-form?
@@ -293,7 +292,7 @@
 ;; --------------------------------------------------------------------------
 ;;
 ;; Inherited from render.sx:
-;;   escape-html, escape-attr, raw-html-content, style-value?, style-value-class
+;;   escape-html, escape-attr, raw-html-content
 ;;
 ;; From eval.sx:
 ;;   eval-expr, trampoline, expand-macro, process-bindings, eval-cond