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>

sx/sxc/pages/__init__.py

@@ -30,8 +30,8 @@ def _register_sx_layouts() -> None:
     """Register the sx docs layout presets."""
     from shared.sx.layouts import register_custom_layout
 
-    register_custom_layout("sx", _sx_full_headers, _sx_oob_headers)
-    register_custom_layout("sx-section", _sx_section_full_headers, _sx_section_oob_headers)
+    register_custom_layout("sx", _sx_full_headers, _sx_oob_headers, _sx_mobile)
+    register_custom_layout("sx-section", _sx_section_full_headers, _sx_section_oob_headers, _sx_section_mobile)
 
 
 def _sx_full_headers(ctx: dict, **kw: Any) -> str:
@@ -98,6 +98,47 @@ def _sx_section_oob_headers(ctx: dict, **kw: Any) -> str:
     return oob_header_sx("root-header-child", "sx-header-child", rows)
 
 
+def _sx_mobile(ctx: dict, **kw: Any) -> str:
+    """Mobile menu for sx home page: main nav + root."""
+    from shared.sx.helpers import (
+        mobile_menu_sx, mobile_root_nav_sx, sx_call, SxExpr,
+    )
+    from sxc.sx_components import _main_nav_sx
+
+    main_nav = _main_nav_sx(kw.get("section"))
+    return mobile_menu_sx(
+        sx_call("mobile-menu-section",
+            label="sx", href="/", level=1, colour="violet",
+            items=SxExpr(main_nav)),
+        mobile_root_nav_sx(ctx),
+    )
+
+
+def _sx_section_mobile(ctx: dict, **kw: Any) -> str:
+    """Mobile menu for sx section pages: sub nav + main nav + root."""
+    from shared.sx.helpers import (
+        mobile_menu_sx, mobile_root_nav_sx, sx_call, SxExpr,
+    )
+    from sxc.sx_components import _main_nav_sx
+
+    section = kw.get("section", "")
+    sub_label = kw.get("sub_label", section)
+    sub_href = kw.get("sub_href", "/")
+    sub_nav = kw.get("sub_nav", "")
+    main_nav = _main_nav_sx(section)
+
+    parts = []
+    if sub_nav:
+        parts.append(sx_call("mobile-menu-section",
+            label=sub_label, href=sub_href, level=2, colour="violet",
+            items=SxExpr(sub_nav)))
+    parts.append(sx_call("mobile-menu-section",
+        label="sx", href="/", level=1, colour="violet",
+        items=SxExpr(main_nav)))
+    parts.append(mobile_root_nav_sx(ctx))
+    return mobile_menu_sx(*parts)
+
+
 # ---------------------------------------------------------------------------
 # Page helpers — Python functions callable from defpage content expressions
 # ---------------------------------------------------------------------------

sx/sxc/pages/docs.sx

@@ -15,6 +15,17 @@
 ;; Docs section
 ;; ---------------------------------------------------------------------------
 
+(defpage docs-index
+  :path "/docs/"
+  :auth :public
+  :layout (:sx-section
+    :section "Docs"
+    :sub-label "Docs"
+    :sub-href "/docs/introduction"
+    :sub-nav (docs-nav "Introduction")
+    :selected "Introduction")
+  :content (docs-content "introduction"))
+
 (defpage docs-page
   :path "/docs/<slug>"
   :auth :public
@@ -56,6 +67,17 @@
 ;; Protocols section
 ;; ---------------------------------------------------------------------------
 
+(defpage protocols-index
+  :path "/protocols/"
+  :auth :public
+  :layout (:sx-section
+    :section "Protocols"
+    :sub-label "Protocols"
+    :sub-href "/protocols/wire-format"
+    :sub-nav (protocols-nav "Wire Format")
+    :selected "Wire Format")
+  :content (protocol-content "wire-format"))
+
 (defpage protocol-page
   :path "/protocols/<slug>"
   :auth :public
@@ -71,6 +93,17 @@
 ;; Examples section
 ;; ---------------------------------------------------------------------------
 
+(defpage examples-index
+  :path "/examples/"
+  :auth :public
+  :layout (:sx-section
+    :section "Examples"
+    :sub-label "Examples"
+    :sub-href "/examples/click-to-load"
+    :sub-nav (examples-nav "Click to Load")
+    :selected "Click to Load")
+  :content (examples-content "click-to-load"))
+
 (defpage examples-page
   :path "/examples/<slug>"
   :auth :public
@@ -86,6 +119,17 @@
 ;; Essays section
 ;; ---------------------------------------------------------------------------
 
+(defpage essays-index
+  :path "/essays/"
+  :auth :public
+  :layout (:sx-section
+    :section "Essays"
+    :sub-label "Essays"
+    :sub-href "/essays/sx-sucks"
+    :sub-nav (essays-nav "sx sucks")
+    :selected "sx sucks")
+  :content (essay-content "sx-sucks"))
+
 (defpage essay-page
   :path "/essays/<slug>"
   :auth :public