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/css_registry.py

@@ -147,48 +147,6 @@ def scan_classes_from_sx(source: str) -> set[str]:
     return classes
 
 
-def register_generated_rule(style_val: Any) -> None:
-    """Register a generated StyleValue's CSS rules in the registry.
-
-    This allows generated class names (``sx-a3f2c1``) to flow through
-    the existing ``lookup_rules()`` → ``SX-Css`` delta pipeline.
-    """
-    from .style_dict import CHILD_SELECTOR_ATOMS
-    cn = style_val.class_name
-    if cn in _REGISTRY:
-        return  # already registered
-
-    parts: list[str] = []
-
-    # Base declarations
-    if style_val.declarations:
-        parts.append(f".{cn}{{{style_val.declarations}}}")
-
-    # Pseudo-class rules
-    for sel, decls in style_val.pseudo_rules:
-        if sel.startswith("::"):
-            parts.append(f".{cn}{sel}{{{decls}}}")
-        elif "&" in sel:
-            # group-hover pattern: ":is(.group:hover) &" → .group:hover .sx-abc
-            expanded = sel.replace("&", f".{cn}")
-            parts.append(f"{expanded}{{{decls}}}")
-        else:
-            parts.append(f".{cn}{sel}{{{decls}}}")
-
-    # Media-query rules
-    for query, decls in style_val.media_rules:
-        parts.append(f"@media {query}{{.{cn}{{{decls}}}}}")
-
-    # Keyframes
-    for _name, kf_rule in style_val.keyframes:
-        parts.append(kf_rule)
-
-    rule_text = "".join(parts)
-    order = len(_RULE_ORDER) + 10000  # after all tw.css rules
-    _REGISTRY[cn] = rule_text
-    _RULE_ORDER[cn] = order
-
-
 def registry_loaded() -> bool:
     """True if the registry has been populated."""
     return bool(_REGISTRY)