Rebrand sexp → sx across web platform (173 files)

Rename all sexp directories, files, identifiers, and references to sx.
artdag/ excluded (separate media processing DSL).

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

cart/bp/fragments/routes.py

@@ -1,6 +1,6 @@
 """Cart app fragment endpoints.
 
-Exposes sexp fragments at ``/internal/fragments/<type>`` for consumption
+Exposes sx fragments at ``/internal/fragments/<type>`` for consumption
 by other coop apps via the fragment client.
 
 Fragments:
@@ -19,13 +19,13 @@ def register():
     bp = Blueprint("fragments", __name__, url_prefix="/internal/fragments")
 
     # ---------------------------------------------------------------
-    # Fragment handlers — return sexp source text
+    # Fragment handlers — return sx source text
     # ---------------------------------------------------------------
 
     async def _cart_mini():
         from shared.services.registry import services
         from shared.infrastructure.urls import blog_url, cart_url
-        from shared.sexp.helpers import sexp_call
+        from shared.sx.helpers import sx_call
 
         user_id = request.args.get("user_id", type=int)
         session_id = request.args.get("session_id")
@@ -35,7 +35,7 @@ def register():
         )
         count = summary.count + summary.calendar_count + summary.ticket_count
         oob = request.args.get("oob", "")
-        return sexp_call("cart-mini",
+        return sx_call("cart-mini",
                          cart_count=count,
                          blog_url=blog_url(""),
                          cart_url=cart_url(""),
@@ -43,9 +43,9 @@ def register():
 
     async def _account_nav_item():
         from shared.infrastructure.urls import cart_url
-        from shared.sexp.helpers import sexp_call
+        from shared.sx.helpers import sx_call
 
-        return sexp_call("account-nav-item",
+        return sx_call("account-nav-item",
                          href=cart_url("/orders/"),
                          label="orders")
 
@@ -67,8 +67,8 @@ def register():
     async def get_fragment(fragment_type: str):
         handler = _handlers.get(fragment_type)
         if handler is None:
-            return Response("", status=200, content_type="text/sexp")
+            return Response("", status=200, content_type="text/sx")
         src = await handler()
-        return Response(src, status=200, content_type="text/sexp")
+        return Response(src, status=200, content_type="text/sx")
 
     return bp