Send all responses as sexp wire format with client-side rendering

- Server sends sexp source text, client (sexp.js) renders everything
- SexpExpr marker class for nested sexp composition in serialize()
- sexp_page() HTML shell with data-mount="body" for full page loads
- sexp_response() returns text/sexp for OOB/partial responses
- ~app-body layout component replaces ~app-layout (no raw!)
- ~rich-text is the only component using raw! (for CMS HTML content)
- Fragment endpoints return text/sexp, auto-wrapped in SexpExpr
- All _*_html() helpers converted to _*_sexp() returning sexp source
- Head auto-hoist: sexp.js moves meta/title/link/script[ld+json]
  from rendered body to document.head automatically
- Unknown components render warning box instead of crashing page
- Component kwargs preserve AST for lazy rendering (fixes <> in kwargs)
- Fix unterminated paren in events/sexp/tickets.sexpr

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

shared/sexp/page.py

@@ -88,7 +88,7 @@ async def render_sexp_response(source: str, **kwargs: Any) -> str:
     """Render an s-expression with the full app template context.
 
     Calls the app's registered context processors (which provide
-    cart_mini_html, auth_menu_html, nav_tree_html, asset_url, etc.)
+    cart_mini, auth_menu, nav_tree, asset_url, etc.)
     and merges them with the caller's kwargs before rendering.
 
     Returns the rendered HTML string (caller wraps in Response as needed).