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/bp/blog/admin/routes.py

@@ -15,6 +15,7 @@ from sqlalchemy import select, delete
 from shared.browser.app.authz import require_admin
 from shared.browser.app.utils.htmx import is_htmx_request
 from shared.browser.app.redis_cacher import invalidate_tag_cache
+from shared.sexp.helpers import sexp_response
 
 from models.tag_group import TagGroup, TagGroupTag
 from models.ghost_content import Tag
@@ -65,7 +66,7 @@ def register():
         if not is_htmx_request():
             return await make_response(await render_tag_groups_page(tctx))
         else:
-            return await make_response(await render_tag_groups_oob(tctx))
+            return sexp_response(await render_tag_groups_oob(tctx))
 
     @bp.post("/")
     @require_admin
@@ -130,7 +131,7 @@ def register():
         if not is_htmx_request():
             return await make_response(await render_tag_group_edit_page(tctx))
         else:
-            return await make_response(await render_tag_group_edit_oob(tctx))
+            return sexp_response(await render_tag_group_edit_oob(tctx))
 
     @bp.post("/<int:id>/")
     @require_admin