Migrate all apps to defpage declarative page routes

Replace Python GET page handlers with declarative defpage definitions in .sx
files across all 8 apps (sx docs, orders, account, market, cart, federation,
events, blog). Each app now has sxc/pages/ with setup functions, layout
registrations, page helpers, and .sx defpage declarations.

Core infrastructure: add g I/O primitive, PageDef support for auth/layout/
data/content/filter/aside/menu slots, post_author auth level, and custom
layout registration. Remove ~1400 lines of render_*_page/render_*_oob
boilerplate. Update all endpoint references in routes, sx_components, and
templates to defpage_* naming.

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

cart/sxc/pages/__init__.py

@@ -0,0 +1,121 @@
+"""Cart defpage setup — registers layouts, page helpers, and loads .sx pages."""
+from __future__ import annotations
+
+from typing import Any
+
+
+def setup_cart_pages() -> None:
+    """Register cart-specific layouts, page helpers, and load page definitions."""
+    _register_cart_layouts()
+    _register_cart_helpers()
+    _load_cart_page_files()
+
+
+def _load_cart_page_files() -> None:
+    import os
+    from shared.sx.pages import load_page_dir
+    load_page_dir(os.path.dirname(__file__), "cart")
+
+
+# ---------------------------------------------------------------------------
+# Layouts
+# ---------------------------------------------------------------------------
+
+def _register_cart_layouts() -> None:
+    from shared.sx.layouts import register_custom_layout
+    register_custom_layout("cart-page", _cart_page_full, _cart_page_oob)
+    register_custom_layout("cart-admin", _cart_admin_full, _cart_admin_oob)
+
+
+def _cart_page_full(ctx: dict, **kw: Any) -> str:
+    from shared.sx.helpers import root_header_sx, sx_call, SxExpr
+    from sx.sx_components import _cart_header_sx, _page_cart_header_sx
+
+    page_post = ctx.get("page_post")
+    root_hdr = root_header_sx(ctx)
+    child = _cart_header_sx(ctx)
+    page_hdr = _page_cart_header_sx(ctx, page_post)
+    nested = sx_call(
+        "header-child-sx",
+        inner=SxExpr("(<> " + child + " " + sx_call("header-child-sx", id="cart-header-child", inner=SxExpr(page_hdr)) + ")"),
+    )
+    return "(<> " + root_hdr + " " + nested + ")"
+
+
+def _cart_page_oob(ctx: dict, **kw: Any) -> str:
+    from shared.sx.helpers import root_header_sx, sx_call, SxExpr
+    from sx.sx_components import _cart_header_sx, _page_cart_header_sx
+
+    page_post = ctx.get("page_post")
+    child_oob = sx_call("oob-header-sx",
+                           parent_id="cart-header-child",
+                           row=SxExpr(_page_cart_header_sx(ctx, page_post)))
+    cart_hdr_oob = _cart_header_sx(ctx, oob=True)
+    root_hdr_oob = root_header_sx(ctx, oob=True)
+    return "(<> " + child_oob + " " + cart_hdr_oob + " " + root_hdr_oob + ")"
+
+
+async def _cart_admin_full(ctx: dict, **kw: Any) -> str:
+    from shared.sx.helpers import root_header_sx
+    from sx.sx_components import _post_header_sx, _cart_page_admin_header_sx
+
+    page_post = ctx.get("page_post")
+    selected = kw.get("selected", "")
+    root_hdr = root_header_sx(ctx)
+    post_hdr = await _post_header_sx(ctx, page_post)
+    admin_hdr = _cart_page_admin_header_sx(ctx, page_post, selected=selected)
+    return "(<> " + root_hdr + " " + post_hdr + " " + admin_hdr + ")"
+
+
+async def _cart_admin_oob(ctx: dict, **kw: Any) -> str:
+    from sx.sx_components import _cart_page_admin_header_sx
+
+    page_post = ctx.get("page_post")
+    selected = kw.get("selected", "")
+    return _cart_page_admin_header_sx(ctx, page_post, oob=True, selected=selected)
+
+
+# ---------------------------------------------------------------------------
+# Page helpers
+# ---------------------------------------------------------------------------
+
+def _register_cart_helpers() -> None:
+    from shared.sx.pages import register_page_helpers
+
+    register_page_helpers("cart", {
+        "overview-content": _h_overview_content,
+        "page-cart-content": _h_page_cart_content,
+        "cart-admin-content": _h_cart_admin_content,
+        "cart-payments-content": _h_cart_payments_content,
+    })
+
+
+def _h_overview_content():
+    from quart import g
+    page_groups = getattr(g, "overview_page_groups", [])
+    from sx.sx_components import _overview_main_panel_sx
+    # _overview_main_panel_sx needs ctx for url helpers — use g-based approach
+    # The function reads cart_url from ctx, which we can get from template context
+    from shared.sx.page import get_template_context
+    import asyncio
+    # Page helpers are sync — we pre-compute in before_request
+    return getattr(g, "overview_content", "")
+
+
+def _h_page_cart_content():
+    from quart import g
+    return getattr(g, "page_cart_content", "")
+
+
+def _h_cart_admin_content():
+    from sx.sx_components import _cart_admin_main_panel_sx
+    from shared.sx.page import get_template_context
+    # Sync helper — _cart_admin_main_panel_sx is sync, but needs ctx
+    # We can pre-compute in before_request, or use get_template_context_sync-like pattern
+    from quart import g
+    return getattr(g, "cart_admin_content", "")
+
+
+def _h_cart_payments_content():
+    from quart import g
+    return getattr(g, "cart_payments_content", "")

cart/sxc/pages/cart.sx

@@ -0,0 +1,25 @@
+;; Cart app defpage declarations.
+
+(defpage cart-overview
+  :path "/"
+  :auth :public
+  :layout :root
+  :content (overview-content))
+
+(defpage page-cart-view
+  :path "/"
+  :auth :public
+  :layout :cart-page
+  :content (page-cart-content))
+
+(defpage cart-admin
+  :path "/"
+  :auth :admin
+  :layout :cart-admin
+  :content (cart-admin-content))
+
+(defpage cart-payments
+  :path "/payments/"
+  :auth :admin
+  :layout (:cart-admin :selected "payments")
+  :content (cart-payments-content))