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/primitives.sx

@@ -541,18 +541,6 @@
 ;; Stdlib — Style
 ;; --------------------------------------------------------------------------
 
-(define-module :stdlib.style)
-
-(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.")
 
 
 ;; --------------------------------------------------------------------------