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>

sx/app.py

@@ -3,28 +3,41 @@ import path_setup  # noqa: F401
 import sxc.sx_components as sx_components  # noqa: F401
 
 from shared.infrastructure.factory import create_base_app
-from shared.sx.jinja_bridge import render
 
 from bp import register_pages
 from services import register_domain_services
 
 
 async def sx_docs_context() -> dict:
-    """SX docs app context processor — minimal, no cross-service fragments."""
+    """SX docs app context processor — fetches cross-service fragments."""
+    from quart import request, g
     from shared.infrastructure.context import base_context
+    from shared.infrastructure.cart_identity import current_cart_identity
+    from shared.infrastructure.fragments import fetch_fragments
 
     ctx = await base_context()
     ctx["menu_items"] = []
-    blog_url = ctx.get("blog_url", "")
-    if callable(blog_url):
-        blog_url_str = blog_url("")
-    else:
-        blog_url_str = str(blog_url or "")
-    ctx["cart_mini"] = render(
-        "cart-mini", cart_count=0, blog_url=blog_url_str, cart_url="",
-    )
-    ctx["auth_menu"] = ""
-    ctx["nav_tree"] = ""
+
+    ident = current_cart_identity()
+    user = getattr(g, "user", None)
+
+    cart_params = {}
+    if ident.get("user_id"):
+        cart_params["user_id"] = ident["user_id"]
+    if ident.get("session_id"):
+        cart_params["session_id"] = ident["session_id"]
+
+    auth_params = {"email": user.email} if user else None
+
+    cart_mini, auth_menu, nav_tree = await fetch_fragments([
+        ("cart", "cart-mini", cart_params or None),
+        ("account", "auth-menu", auth_params),
+        ("blog", "nav-tree", {"app_name": "sx", "path": request.path}),
+    ], required=False)
+    ctx["cart_mini"] = cart_mini
+    ctx["auth_menu"] = auth_menu
+    ctx["nav_tree"] = nav_tree
+
     return ctx