Add OOB header swaps for sx docs navigation + enable OAuth + fragments

- OOB nav updates: AJAX navigation now swaps both menu bar levels
  (main nav highlighting + sub-nav with current page) using the same
  oob_header_sx/oob_page_sx pattern as blog/market/events
- Enable OAuth for sx and test apps (removed from _NO_OAUTH, added sx
  to ALLOWED_CLIENTS, added app_urls for sx/test/orders)
- Fetch real cross-service fragments (cart-mini, auth-menu, nav-tree)
  instead of hardcoding empty values
- Add :selected param to ~menu-row-sx for white text current-page label
- Fix duplicate element IDs: use menu-row-sx child_id/child mechanism
  instead of manual header_child_sx wrappers
- Fix home page copy: "Server-rendered DOM over the wire (no HTML)"

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

shared/infrastructure/factory.py

@@ -145,8 +145,8 @@ def create_base_app(
     errors(app)
 
     # Auto-register OAuth client blueprint for non-account apps
-    # (account is the OAuth authorization server; test/sx are public dashboards)
-    _NO_OAUTH = {"account", "test", "sx"}
+    # (account is the OAuth authorization server)
+    _NO_OAUTH = {"account"}
     if name not in _NO_OAUTH:
         from shared.infrastructure.oauth import create_oauth_blueprint
         app.register_blueprint(create_oauth_blueprint(name))

shared/sx/templates/layout.sx

@@ -82,9 +82,9 @@
     (div :class "block md:hidden text-md font-bold"
       (when auth-menu auth-menu))))
 
-; @css bg-sky-400 bg-sky-300 bg-sky-200 bg-sky-100
+; @css bg-sky-400 bg-sky-300 bg-sky-200 bg-sky-100 bg-violet-400 bg-violet-300 bg-violet-200 bg-violet-100
 (defcomp ~menu-row-sx (&key id level colour link-href link-label link-label-content icon
-                             hx-select nav child-id child oob external)
+                             selected hx-select nav child-id child oob external)
   (let* ((c (or colour "sky"))
          (lv (or level 1))
          (shade (str (- 500 (* lv 100)))))
@@ -102,7 +102,10 @@
              :class "w-full whitespace-normal flex items-center gap-2 font-bold text-2xl px-3 py-2"
             (when icon (i :class icon :aria-hidden "true"))
             (if link-label-content link-label-content
-              (when link-label (div link-label)))))
+              (<>
+                (when link-label (div link-label))
+                (when selected
+                  (span :class "text-lg text-white/80 font-normal" selected))))))
         (when nav
           (nav :class "hidden md:flex gap-4 text-sm ml-2 justify-end items-center flex-0"
             nav)))