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>

market/bp/product/routes.py

@@ -19,6 +19,7 @@ from shared.browser.app.redis_cacher import cache_page, clear_cache
 from ..cart.services import total
 from shared.infrastructure.actions import call_action
 from .services.product_operations import massage_full_product
+from shared.sexp.helpers import sexp_response
 
 
 def register():
@@ -115,10 +116,10 @@ def register():
         tctx["liked_by_current_user"] = item_data.get("liked", False)
         if not is_htmx_request():
             html = await render_product_page(tctx, d)
+            return html
         else:
-            html = await render_product_oob(tctx, d)
-
-        return html
+            sexp_src = await render_product_oob(tctx, d)
+            return sexp_response(sexp_src)
 
     @bp.post("/like/toggle/")
     @clear_cache(tag="browse", tag_scope="user")
@@ -128,9 +129,7 @@ def register():
       from sexp.sexp_components import render_like_toggle_button
 
       if not g.user:
-          html = render_like_toggle_button(product_slug, False)
-          resp = make_response(html, 403)
-          return resp
+          return sexp_response(render_like_toggle_button(product_slug, False), status=403)
 
       user_id = g.user.id
 
@@ -139,7 +138,7 @@ def register():
       })
       liked = result["liked"]
 
-      return render_like_toggle_button(product_slug, liked)
+      return sexp_response(render_like_toggle_button(product_slug, liked))
 
 
 
@@ -156,10 +155,10 @@ def register():
       tctx["liked_by_current_user"] = item_data.get("liked", False)
       if not is_htmx_request():
           html = await render_product_admin_page(tctx, d)
+          return await make_response(html)
       else:
-          html = await render_product_admin_oob(tctx, d)
-
-      return await make_response(html)
+          sexp_src = await render_product_admin_oob(tctx, d)
+          return sexp_response(sexp_src)
     
     
     from bp.cart.services.identity import current_cart_identity
@@ -254,11 +253,11 @@ def register():
         )
 
         # htmx response: OOB-swap mini cart + product buttons
-        if request.headers.get("HX-Request") == "true":
+        if request.headers.get("SX-Request") == "true" or request.headers.get("HX-Request") == "true":
             from sexp.sexp_components import render_cart_added_response
             item_data = getattr(g, "item_data", {})
             d = item_data.get("d", {})
-            return render_cart_added_response(g.cart, ci_ns, d)
+            return sexp_response(render_cart_added_response(g.cart, ci_ns, d))
 
         # normal POST: go to cart page
         from shared.infrastructure.urls import cart_url