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/boundary.py

@@ -94,10 +94,10 @@ def validate_helper(service: str, name: str) -> None:
 def validate_boundary_value(value: Any, context: str = "") -> None:
     """Validate that a value is an allowed SX boundary type.
 
-    Allowed: int, float, str, bool, None/NIL, list, dict, SxExpr, StyleValue.
+    Allowed: int, float, str, bool, None/NIL, list, dict, SxExpr.
     NOT allowed: datetime, ORM models, Quart objects, raw callables.
     """
-    from .types import NIL, StyleValue
+    from .types import NIL
     from .parser import SxExpr
 
     if value is None or value is NIL:
@@ -106,8 +106,6 @@ def validate_boundary_value(value: Any, context: str = "") -> None:
         return
     if isinstance(value, SxExpr):
         return
-    if isinstance(value, StyleValue):
-        return
     if isinstance(value, list):
         for item in value:
             validate_boundary_value(item, context)