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>

blog/sexp/header.sexpr

@@ -3,9 +3,9 @@
 (defcomp ~blog-header-label ()
   (div))
 
-(defcomp ~blog-container-nav (&key container-nav-html)
+(defcomp ~blog-container-nav (&key container-nav)
   (div :class "flex flex-col sm:flex-row sm:items-center gap-2 border-r border-stone-200 mr-2 sm:max-w-2xl"
-    :id "entries-calendars-nav-wrapper" (raw! container-nav-html)))
+    :id "entries-calendars-nav-wrapper" container-nav))
 
 (defcomp ~blog-admin-label ()
   (<> (i :class "fa fa-shield-halved" :aria-hidden "true") " admin"))